Functions for Working with Dictionaries

Note

For dictionaries created with DDL queries, the dict_name parameter must be fully specified, like <database>.<dict_name>. Otherwise, the current database is used.

For information on connecting and configuring dictionaries, see Dictionaries.

Example dictionaries

The examples in this section make use of the following dictionaries. You can create them in ClickHouse to run the examples for the functions described below.

Example dictionary for dictGet<T> and dictGet<T>OrDefault functions

-- Create table with all the required data types
CREATE TABLE all_types_test (
    `id` UInt32,
    
    -- String type
    `String_value` String,
    
    -- Unsigned integer types
    `UInt8_value` UInt8,
    `UInt16_value` UInt16,
    `UInt32_value` UInt32,
    `UInt64_value` UInt64,
    
    -- Signed integer types
    `Int8_value` Int8,
    `Int16_value` Int16,
    `Int32_value` Int32,
    `Int64_value` Int64,
    
    -- Floating point types
    `Float32_value` Float32,
    `Float64_value` Float64,
    
    -- Date/time types
    `Date_value` Date,
    `DateTime_value` DateTime,
    
    -- Network types
    `IPv4_value` IPv4,
    `IPv6_value` IPv6,
    
    -- UUID type
    `UUID_value` UUID
) ENGINE = MergeTree() 
ORDER BY id;

-- Insert test data
INSERT INTO all_types_test VALUES
(
    1,                              -- id
    'ClickHouse',                   -- String
    100,                            -- UInt8
    5000,                           -- UInt16
    1000000,                        -- UInt32
    9223372036854775807,            -- UInt64
    -100,                           -- Int8
    -5000,                          -- Int16
    -1000000,                       -- Int32
    -9223372036854775808,           -- Int64
    123.45,                         -- Float32
    987654.123456,                  -- Float64
    '2024-01-15',                   -- Date
    '2024-01-15 10:30:00',          -- DateTime
    '192.168.1.1',                  -- IPv4
    '2001:db8::1',                  -- IPv6
    '550e8400-e29b-41d4-a716-446655440000' -- UUID
)

-- Create dictionary
CREATE DICTIONARY all_types_dict
(
    id UInt32,
    String_value String,
    UInt8_value UInt8,
    UInt16_value UInt16,
    UInt32_value UInt32,
    UInt64_value UInt64,
    Int8_value Int8,
    Int16_value Int16,
    Int32_value Int32,
    Int64_value Int64,
    Float32_value Float32,
    Float64_value Float64,
    Date_value Date,
    DateTime_value DateTime,
    IPv4_value IPv4,
    IPv6_value IPv6,
    UUID_value UUID
)
PRIMARY KEY id
SOURCE(CLICKHOUSE(HOST 'localhost' PORT 9000 USER 'default' TABLE 'all_types_test' DB 'default'))
LAYOUT(HASHED())
LIFETIME(MIN 300 MAX 600);

Example dictionary for dictGetAll

Create a table to store the data for the regexp tree dictionary:

CREATE TABLE regexp_os(
    id UInt64,
    parent_id UInt64,
    regexp String,
    keys Array(String),
    values Array(String)
)
ENGINE = Memory;

Insert data into the table:

INSERT INTO regexp_os 
SELECT *
FROM s3(
    'https://datasets-documentation.s3.eu-west-3.amazonaws.com/' ||
    'user_agent_regex/regexp_os.csv'
);

Create the regexp tree dictionary:

CREATE DICTIONARY regexp_tree
(
    regexp String,
    os_replacement String DEFAULT 'Other',
    os_v1_replacement String DEFAULT '0',
    os_v2_replacement String DEFAULT '0',
    os_v3_replacement String DEFAULT '0',
    os_v4_replacement String DEFAULT '0'
)
PRIMARY KEY regexp
SOURCE(CLICKHOUSE(TABLE 'regexp_os'))
LIFETIME(MIN 0 MAX 0)
LAYOUT(REGEXP_TREE);

Example range key dictionary

Create the input table:

CREATE TABLE range_key_dictionary_source_table
(
    key UInt64,
    start_date Date,
    end_date Date,
    value String,
    value_nullable Nullable(String)
)
ENGINE = TinyLog();

Insert the data into the input table:

INSERT INTO range_key_dictionary_source_table VALUES(1, toDate('2019-05-20'), toDate('2019-05-20'), 'First', 'First');
INSERT INTO range_key_dictionary_source_table VALUES(2, toDate('2019-05-20'), toDate('2019-05-20'), 'Second', NULL);
INSERT INTO range_key_dictionary_source_table VALUES(3, toDate('2019-05-20'), toDate('2019-05-20'), 'Third', 'Third');

Create the dictionary:

CREATE DICTIONARY range_key_dictionary
(
    key UInt64,
    start_date Date,
    end_date Date,
    value String,
    value_nullable Nullable(String)
)
PRIMARY KEY key
SOURCE(CLICKHOUSE(HOST 'localhost' PORT tcpPort() TABLE 'range_key_dictionary_source_table'))
LIFETIME(MIN 1 MAX 1000)
LAYOUT(RANGE_HASHED())
RANGE(MIN start_date MAX end_date);

Example complex key dictionary

Create the source table:

CREATE TABLE dict_mult_source
(
id UInt32,
c1 UInt32,
c2 String
) ENGINE = Memory;

Insert the data into the source table:

INSERT INTO dict_mult_source VALUES
(1, 1, '1'),
(2, 2, '2'),
(3, 3, '3');

Create the dictionary:

CREATE DICTIONARY ext_dict_mult
(
    id UInt32,
    c1 UInt32,
    c2 String
)
PRIMARY KEY id
SOURCE(CLICKHOUSE(HOST 'localhost' PORT 9000 USER 'default' TABLE 'dict_mult_source' DB 'default'))
LAYOUT(FLAT())
LIFETIME(MIN 0 MAX 0);

Example hierarchical dictionary

Create the source table:

CREATE TABLE hierarchy_source
(
  id UInt64,
  parent_id UInt64,
  name String
) ENGINE = Memory;

Insert the data into the source table:

INSERT INTO hierarchy_source VALUES
(0, 0, 'Root'),
(1, 0, 'Level 1 - Node 1'),
(2, 1, 'Level 2 - Node 2'),
(3, 1, 'Level 2 - Node 3'),
(4, 2, 'Level 3 - Node 4'),
(5, 2, 'Level 3 - Node 5'),
(6, 3, 'Level 3 - Node 6');

-- 0 (Root)
-- └── 1 (Level 1 - Node 1)
--     ├── 2 (Level 2 - Node 2)
--     │   ├── 4 (Level 3 - Node 4)
--     │   └── 5 (Level 3 - Node 5)
--     └── 3 (Level 2 - Node 3)
--         └── 6 (Level 3 - Node 6)

Create the dictionary:

CREATE DICTIONARY hierarchical_dictionary
(
    id UInt64,
    parent_id UInt64 HIERARCHICAL,
    name String
)
PRIMARY KEY id
SOURCE(CLICKHOUSE(HOST 'localhost' PORT 9000 USER 'default' TABLE 'hierarchy_source' DB 'default'))
LAYOUT(HASHED())
LIFETIME(MIN 300 MAX 600);

dictGet

Introduced in: v18.16

Retrieves values from a dictionary.

Syntax

dictGet('dict_name', attr_names, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_names — Name of the column of the dictionary, or tuple of column names. String or Tuple(String)
• id_expr — Key value. An expression returning UInt64/Tuple(T). UInt64 or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr if the key is found. If the key is not found, returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Examples

Retrieve a single attribute

SELECT dictGet('ext_dict_test', 'c1', toUInt64(1)) AS val

1

Multiple attributes

SELECT
    dictGet('ext_dict_mult', ('c1','c2'), number + 1) AS val,
    toTypeName(val) AS type
FROM system.numbers
LIMIT 3;

┌─val─────┬─type───────────┐
│ (1,'1') │ Tuple(        ↴│
│         │↳    c1 UInt32,↴│
│         │↳    c2 String) │
│ (2,'2') │ Tuple(        ↴│
│         │↳    c1 UInt32,↴│
│         │↳    c2 String) │
│ (3,'3') │ Tuple(        ↴│
│         │↳    c1 UInt32,↴│
│         │↳    c2 String) │
└─────────┴────────────────┘

dictGetAll

Introduced in: v23.5

Converts a dictionary attribute value to All data type regardless of the dictionary configuration.

Syntax

dictGetAll(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT
    'Mozilla/5.0 (Linux; Android 12; SM-G998B) Mobile Safari/537.36' AS user_agent,

    -- This will match ALL applicable patterns
    dictGetAll('regexp_tree', 'os_replacement', 'Mozilla/5.0 (Linux; Android 12; SM-G998B) Mobile Safari/537.36') AS all_matches,

    -- This returns only the first match
    dictGet('regexp_tree', 'os_replacement', 'Mozilla/5.0 (Linux; Android 12; SM-G998B) Mobile Safari/537.36') AS first_match;

┌─user_agent─────────────────────────────────────────────────────┬─all_matches─────────────────────────────┬─first_match─┐
│ Mozilla/5.0 (Linux; Android 12; SM-G998B) Mobile Safari/537.36 │ ['Android','Android','Android','Linux'] │ Android     │
└────────────────────────────────────────────────────────────────┴─────────────────────────────────────────┴─────────────┘

dictGetChildren

Introduced in: v21.4

Returns first-level children as an array of indexes. It is the inverse transformation for dictGetHierarchy.

Syntax

dictGetChildren(dict_name, key)

Arguments

• dict_name — Name of the dictionary. String
• key — Key to be checked. const String

Returned value

Returns the first-level descendants for the key. Array(UInt64)

Examples

Get the first-level children of a dictionary

SELECT dictGetChildren('hierarchical_dictionary', 2);

┌─dictGetChild⋯ionary', 2)─┐
│ [4,5]                    │
└──────────────────────────┘

dictGetDate

Introduced in: v1.1

Converts a dictionary attribute value to Date data type regardless of the dictionary configuration.

Syntax

dictGetDate(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetDate('all_types_dict', 'Date_value', 1)

┌─dictGetDate(⋯_value', 1)─┐
│               2020-01-01 │
└──────────────────────────┘

dictGetDateOrDefault

Introduced in: v1.1

Converts a dictionary attribute value to Date data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetDateOrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetDate('all_types_dict', 'Date_value', 1);

-- for key which does not exist, returns the provided default value
SELECT dictGetDateOrDefault('all_types_dict', 'Date_value', 999, toDate('1970-01-01'));

┌─dictGetDate(⋯_value', 1)─┐
│               2024-01-15 │
└──────────────────────────┘
┌─dictGetDateO⋯70-01-01'))─┐
│               1970-01-01 │
└──────────────────────────┘

dictGetDateTime

Introduced in: v1.1

Converts a dictionary attribute value to DateTime data type regardless of the dictionary configuration.

Syntax

dictGetDateTime(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetDateTime('all_types_dict', 'DateTime_value', 1)

┌─dictGetDateT⋯_value', 1)─┐
│      2024-01-15 10:30:00 │
└──────────────────────────┘

dictGetDateTimeOrDefault

Introduced in: v1.1

Converts a dictionary attribute value to DateTime data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetDateTimeOrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetDateTime('all_types_dict', 'DateTime_value', 1);

-- for key which does not exist, returns the provided default value
SELECT dictGetDateTimeOrDefault('all_types_dict', 'DateTime_value', 999, toDateTime('1970-01-01 00:00:00'));

┌─dictGetDateT⋯_value', 1)─┐
│      2024-01-15 10:30:00 │
└──────────────────────────┘
┌─dictGetDateT⋯0:00:00'))──┐
│      1970-01-01 00:00:00 │
└──────────────────────────┘

dictGetDescendants

Introduced in: v21.4

Returns all descendants as if the dictGetChildren function were applied level times recursively.

Syntax

dictGetDescendants(dict_name, key, level)

Arguments

• dict_name — Name of the dictionary. String
• key — Key to be checked. const String
• level — Key to be checked. Hierarchy level. If level = 0 returns all descendants to the end. UInt8

Returned value

Returns the descendants for the key. Array(UInt64)

Examples

Get the first-level children of a dictionary

-- consider the following hierarchical dictionary:
-- 0 (Root)
-- └── 1 (Level 1 - Node 1)
--     ├── 2 (Level 2 - Node 2)
--     │   ├── 4 (Level 3 - Node 4)
--     │   └── 5 (Level 3 - Node 5)
--     └── 3 (Level 2 - Node 3)
--         └── 6 (Level 3 - Node 6)

SELECT dictGetDescendants('hierarchical_dictionary', 0, 2)

┌─dictGetDesce⋯ary', 0, 2)─┐
│ [3,2]                    │
└──────────────────────────┘

dictGetFloat32

Introduced in: v1.1

Converts a dictionary attribute value to Float32 data type regardless of the dictionary configuration.

Syntax

dictGetFloat32(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetFloat32('all_types_dict', 'Float32_value', 1)

┌─dictGetFloat⋯_value', 1)─┐
│               -123.123   │
└──────────────────────────┘

dictGetFloat32OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to Float32 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetFloat32OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetFloat32('all_types_dict', 'Float32_value', 1);

-- for key which does not exist, returns the provided default value (-1.0)
SELECT dictGetFloat32OrDefault('all_types_dict', 'Float32_value', 999, -1.0);

┌─dictGetFloat⋯_value', 1)─┐
│                   123.45 │
└──────────────────────────┘
┌─dictGetFloat⋯e', 999, -1)─┐
│                       -1  │
└───────────────────────────┘

dictGetFloat64

Introduced in: v1.1

Converts a dictionary attribute value to Float64 data type regardless of the dictionary configuration.

Syntax

dictGetFloat64(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetFloat64('all_types_dict', 'Float64_value', 1)

┌─dictGetFloat⋯_value', 1)─┐
│                 -123.123 │
└──────────────────────────┘

dictGetFloat64OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to Float64 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetFloat64OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetFloat64('all_types_dict', 'Float64_value', 1);

-- for key which does not exist, returns the provided default value (nan)
SELECT dictGetFloat64OrDefault('all_types_dict', 'Float64_value', 999, nan);

┌─dictGetFloat⋯_value', 1)─┐
│            987654.123456 │
└──────────────────────────┘
┌─dictGetFloat⋯, 999, nan)─┐
│                      nan │
└──────────────────────────┘

dictGetHierarchy

Introduced in: v1.1

Creates an array, containing all the parents of a key in the hierarchical dictionary.

Syntax

dictGetHierarchy(dict_name, key)

Arguments

• dict_name — Name of the dictionary. String
• key — Key value. const String

Returned value

Returns parents for the key. Array(UInt64)

Examples

Get hierarchy for a key

SELECT dictGetHierarchy('hierarchical_dictionary', 5)

┌─dictGetHiera⋯ionary', 5)─┐
│ [5,2,1]                  │
└──────────────────────────┘

dictGetIPv4

Introduced in: v1.1

Converts a dictionary attribute value to IPv4 data type regardless of the dictionary configuration.

Syntax

dictGetIPv4(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetIPv4('all_types_dict', 'IPv4_value', 1)

┌─dictGetIPv4('all_⋯ 'IPv4_value', 1)─┐
│ 192.168.0.1                         │
└─────────────────────────────────────┘

dictGetIPv4OrDefault

Introduced in: v23.1

Converts a dictionary attribute value to IPv4 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetIPv4OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetIPv4('all_types_dict', 'IPv4_value', 1);

-- for key which does not exist, returns the provided default value
SELECT dictGetIPv4OrDefault('all_types_dict', 'IPv4_value', 999, toIPv4('0.0.0.0'));

┌─dictGetIPv4('all_⋯ 'IPv4_value', 1)─┐
│ 192.168.0.1                         │
└─────────────────────────────────────┘
┌─dictGetIPv4OrDefa⋯0.0.0.0'))─┐
│ 0.0.0.0                      │
└──────────────────────────────┘

dictGetIPv6

Introduced in: v23.1

Converts a dictionary attribute value to IPv6 data type regardless of the dictionary configuration.

Syntax

dictGetIPv6(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetIPv6('all_types_dict', 'IPv6_value', 1)

┌─dictGetIPv6('all_⋯ 'IPv6_value', 1)─┐
│ 2001:db8:85a3::8a2e:370:7334        │
└─────────────────────────────────────┘

dictGetIPv6OrDefault

Introduced in: v23.1

Converts a dictionary attribute value to IPv6 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetIPv6OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetIPv6('all_types_dict', 'IPv6_value', 1);

-- for key which does not exist, returns the provided default value
SELECT dictGetIPv6OrDefault('all_types_dict', 'IPv6_value', 999, '::1'::IPv6);

┌─dictGetIPv6('all_⋯ 'IPv6_value', 1)─┐
│ 2001:db8:85a3::8a2e:370:7334        │
└─────────────────────────────────────┘
┌─dictGetIPv6OrDefa⋯:1'::IPv6)─┐
│ ::1                          │
└──────────────────────────────┘

dictGetInt16

Introduced in: v1.1

Converts a dictionary attribute value to Int16 data type regardless of the dictionary configuration.

Syntax

dictGetInt16(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetInt16('all_types_dict', 'Int16_value', 1)

┌─dictGetInt16⋯_value', 1)─┐
│                    -5000 │
└──────────────────────────┘

dictGetInt16OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to Int16 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetInt16OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetInt16('all_types_dict', 'Int16_value', 1);

-- for key which does not exist, returns the provided default value (-1)
SELECT dictGetInt16OrDefault('all_types_dict', 'Int16_value', 999, -1);

┌─dictGetInt16⋯_value', 1)─┐
│                    -5000 │
└──────────────────────────┘
┌─dictGetInt16⋯', 999, -1)─┐
│                       -1 │
└──────────────────────────┘

dictGetInt32

Introduced in: v1.1

Converts a dictionary attribute value to Int32 data type regardless of the dictionary configuration.

Syntax

dictGetInt32(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetInt32('all_types_dict', 'Int32_value', 1)

┌─dictGetInt32⋯_value', 1)─┐
│                -1000000  │
└──────────────────────────┘

dictGetInt32OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to Int32 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetInt32OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetInt32('all_types_dict', 'Int32_value', 1);

-- for key which does not exist, returns the provided default value (-1)
SELECT dictGetInt32OrDefault('all_types_dict', 'Int32_value', 999, -1);

┌─dictGetInt32⋯_value', 1)─┐
│                -1000000  │
└──────────────────────────┘
┌─dictGetInt32⋯', 999, -1)─┐
│                       -1 │
└──────────────────────────┘

dictGetInt64

Introduced in: v1.1

Converts a dictionary attribute value to Int64 data type regardless of the dictionary configuration.

Syntax

dictGetInt64(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetInt64('all_types_dict', 'Int64_value', 1)

┌─dictGetInt64⋯_value', 1)───┐
│       -9223372036854775807 │
└────────────────────────────┘

dictGetInt64OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to Int64 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetInt64OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetInt64('all_types_dict', 'Int64_value', 1);

-- for key which does not exist, returns the provided default value (-1)
SELECT dictGetInt64OrDefault('all_types_dict', 'Int64_value', 999, -1);

┌─dictGetInt64⋯_value', 1)─┐
│     -9223372036854775808 │
└──────────────────────────┘
┌─dictGetInt64⋯', 999, -1)─┐
│                       -1 │
└──────────────────────────┘

dictGetInt8

Introduced in: v1.1

Converts a dictionary attribute value to Int8 data type regardless of the dictionary configuration.

Syntax

dictGetInt8(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetInt8('all_types_dict', 'Int8_value', 1)

┌─dictGetInt8(⋯_value', 1)─┐
│                     -100 │
└──────────────────────────┘

dictGetInt8OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to Int8 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetInt8OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetInt8('all_types_dict', 'Int8_value', 1);

-- for key which does not exist, returns the provided default value (-1)
SELECT dictGetInt8OrDefault('all_types_dict', 'Int8_value', 999, -1);

┌─dictGetInt8(⋯_value', 1)─┐
│                     -100 │
└──────────────────────────┘
┌─dictGetInt8O⋯', 999, -1)─┐
│                       -1 │
└──────────────────────────┘

dictGetKeys

Introduced in: v25.12

Returns the dictionary key(s) whose attribute equals the specified value. This is the inverse of the function dictGet on a single attribute.

Use setting max_reverse_dictionary_lookup_cache_size_bytes to cap the size of the per-query reverse-lookup cache used by dictGetKeys. The cache stores serialized key tuples for each attribute value to avoid re-scanning the dictionary within the same query. The cache is not persistent across queries. When the limit is reached, entries are evicted with LRU. This is most effective with large dictionaries when the input has low cardinality and the working set fits in the cache. Set to 0 to disable caching.

Syntax

dictGetKeys('dict_name', 'attr_name', value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Attribute to match. String
• value_expr — Value to match against the attribute. Expression

Returned value

For single key dictionaries: an array of keys whose attribute equals value_expr. For multi key dictionaries: an array of tuples of keys whose attribute equals value_expr. If there is no attribute corresponding to value_expr in the dictionary, then an empty array is returned. ClickHouse throws an exception if it cannot parse the value of the attribute or the value cannot be converted to the attribute data type.

Examples

Sample usage

SELECT dictGetKeys('task_id_to_priority_dictionary', 'priority_level', 'high') AS ids;

┌─-ids──┐
│ [4,2] │
└───────┘

dictGetOrDefault

Introduced in: v18.16

Retrieves values from a dictionary, with a default value if the key is not found.

Syntax

dictGetOrDefault('dict_name', attr_names, id_expr, default_value)

Arguments

• dict_name — Name of the dictionary. String
• attr_names — Name of the column of the dictionary, or tuple of column names. String or Tuple(String)
• id_expr — Key value. An expression returning UInt64/Tuple(T). UInt64 or Tuple(T)
• default_value — Default value to return if the key is not found. Type must match the attribute's data type.

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr if the key is found. If the key is not found, returns the default_value provided.

Examples

Get value with default

SELECT dictGetOrDefault('ext_dict_mult', 'c1', toUInt64(999), 0) AS val

0

dictGetOrNull

Introduced in: v21.4

Retrieves values from a dictionary, returning NULL if the key is not found.

Syntax

dictGetOrNull('dict_name', 'attr_name', id_expr)

Arguments

• dict_name — Name of the dictionary. String literal. - attr_name — Name of the column to retrieve. String literal. - id_expr — Key value. Expression returning dictionary key-type value.

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr if the key is found. If the key is not found, returns NULL.

Examples

Example using the range key dictionary

SELECT
    (number, toDate('2019-05-20')),
    dictGetOrNull('range_key_dictionary', 'value', number, toDate('2019-05-20')),
FROM system.numbers LIMIT 5 FORMAT TabSeparated;

(0,'2019-05-20')  \N
(1,'2019-05-20')  First
(2,'2019-05-20')  Second
(3,'2019-05-20')  Third
(4,'2019-05-20')  \N

dictGetString

Introduced in: v1.1

Converts a dictionary attribute value to String data type regardless of the dictionary configuration.

Syntax

dictGetString(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetString('all_types_dict', 'String_value', 1)

┌─dictGetString(⋯_value', 1)─┐
│ test string                │
└────────────────────────────┘

dictGetStringOrDefault

Introduced in: v1.1

Converts a dictionary attribute value to String data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetStringOrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetString('all_types_dict', 'String_value', 1);

-- for key which does not exist, returns the provided default value
SELECT dictGetStringOrDefault('all_types_dict', 'String_value', 999, 'default');

┌─dictGetString(⋯_value', 1)─┐
│ test string                │
└────────────────────────────┘
┌─dictGetStringO⋯ 999, 'default')─┐
│ default                         │
└─────────────────────────────────┘

dictGetUInt16

Introduced in: v1.1

Converts a dictionary attribute value to UInt16 data type regardless of the dictionary configuration.

Syntax

dictGetUInt16(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetUInt16('all_types_dict', 'UInt16_value', 1)

┌─dictGetUInt1⋯_value', 1)─┐
│                     5000 │
└──────────────────────────┘

dictGetUInt16OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to UInt16 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetUInt16OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetUInt16('all_types_dict', 'UInt16_value', 1);

-- for key which does not exist, returns the provided default value (0)
SELECT dictGetUInt16OrDefault('all_types_dict', 'UInt16_value', 999, 0);

┌─dictGetUInt1⋯_value', 1)─┐
│                     5000 │
└──────────────────────────┘
┌─dictGetUInt1⋯e', 999, 0)─┐
│                        0 │
└──────────────────────────┘

dictGetUInt32

Introduced in: v1.1

Converts a dictionary attribute value to UInt32 data type regardless of the dictionary configuration.

Syntax

dictGetUInt32(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetUInt32('all_types_dict', 'UInt32_value', 1)

┌─dictGetUInt3⋯_value', 1)─┐
│                  1000000 │
└──────────────────────────┘

dictGetUInt32OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to UInt32 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetUInt32OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetUInt32('all_types_dict', 'UInt32_value', 1);

-- for key which does not exist, returns the provided default value (0)
SELECT dictGetUInt32OrDefault('all_types_dict', 'UInt32_value', 999, 0);

┌─dictGetUInt3⋯_value', 1)─┐
│                  1000000 │
└──────────────────────────┘
┌─dictGetUInt3⋯e', 999, 0)─┐
│                        0 │
└──────────────────────────┘

dictGetUInt64

Introduced in: v1.1

Converts a dictionary attribute value to UInt64 data type regardless of the dictionary configuration.

Syntax

dictGetUInt64(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetUInt64('all_types_dict', 'UInt64_value', 1)

┌─dictGetUInt6⋯_value', 1)─┐
│      9223372036854775807 │
└──────────────────────────┘

dictGetUInt64OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to UInt64 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetUInt64OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetUInt64('all_types_dict', 'UInt64_value', 1);

-- for key which does not exist, returns the provideddefault value (0)
SELECT dictGetUInt64OrDefault('all_types_dict', 'UInt64_value', 999, 0);

┌─dictGetUInt6⋯_value', 1)─┐
│      9223372036854775807 │
└──────────────────────────┘
┌─dictGetUInt6⋯e', 999, 0)─┐
│                        0 │
└──────────────────────────┘

dictGetUInt8

Introduced in: v1.1

Converts a dictionary attribute value to UInt8 data type regardless of the dictionary configuration.

Syntax

dictGetUInt8(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetUInt8('all_types_dict', 'UInt8_value', 1)

┌─dictGetUInt8⋯_value', 1)─┐
│                      100 │
└──────────────────────────┘

dictGetUInt8OrDefault

Introduced in: v1.1

Converts a dictionary attribute value to UInt8 data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetUInt8OrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetUInt8('all_types_dict', 'UInt8_value', 1);

-- for key which does not exist, returns the provided default value (0)
SELECT dictGetUInt8OrDefault('all_types_dict', 'UInt8_value', 999, 0);

┌─dictGetUInt8⋯_value', 1)─┐
│                      100 │
└──────────────────────────┘
┌─dictGetUInt8⋯e', 999, 0)─┐
│                        0 │
└──────────────────────────┘

dictGetUUID

Introduced in: v1.1

Converts a dictionary attribute value to UUID data type regardless of the dictionary configuration.

Syntax

dictGetUUID(dict_name, attr_name, id_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. An expression returning a dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the content of the <null_value> element specified for the attribute in the dictionary configuration.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

SELECT dictGetUUID('all_types_dict', 'UUID_value', 1)

┌─dictGetUUID(⋯_value', 1)─────────────┐
│ 123e4567-e89b-12d3-a456-426614174000 │
└──────────────────────────────────────┘

dictGetUUIDOrDefault

Introduced in: v1.1

Converts a dictionary attribute value to UUID data type regardless of the dictionary configuration, or returns the provided default value if the key is not found.

Syntax

dictGetUUIDOrDefault(dict_name, attr_name, id_expr, default_value_expr)

Arguments

• dict_name — Name of the dictionary. String
• attr_name — Name of the column of the dictionary. String or Tuple(String)
• id_expr — Key value. Expression returning dictionary key-type value or tuple value (dictionary configuration dependent). Expression or Tuple(T)
• default_value_expr — Value(s) returned if the dictionary does not contain a row with the id_expr key. Expression or Tuple(T)

Returned value

Returns the value of the dictionary attribute that corresponds to id_expr, otherwise returns the value passed as the default_value_expr parameter.

Note

ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.

Examples

Usage example

-- for key which exists
SELECT dictGetUUID('all_types_dict', 'UUID_value', 1);

-- for key which does not exist, returns the provided default value
SELECT dictGetUUIDOrDefault('all_types_dict', 'UUID_value', 999, '00000000-0000-0000-0000-000000000000'::UUID);

┌─dictGetUUID('all_t⋯ 'UUID_value', 1)─┐
│ 550e8400-e29b-41d4-a716-446655440000 │
└──────────────────────────────────────┘
┌─dictGetUUIDOrDefa⋯000000000000'::UUID)─┐
│ 00000000-0000-0000-0000-000000000000   │
└────────────────────────────────────────┘

dictHas

Introduced in: v1.1

Checks whether a key is present in a dictionary.

Syntax

dictHas('dict_name', id_expr)

Arguments

• dict_name — Name of the dictionary. String
• id_expr — Key value const String

Returned value

Returns 1 if the key exists, otherwise 0. UInt8

Examples

Check for the existence of a key in a dictionary

-- consider the following hierarchical dictionary:
-- 0 (Root)
-- └── 1 (Level 1 - Node 1)
--     ├── 2 (Level 2 - Node 2)
--     │   ├── 4 (Level 3 - Node 4)
--     │   └── 5 (Level 3 - Node 5)
--     └── 3 (Level 2 - Node 3)
--         └── 6 (Level 3 - Node 6)

SELECT dictHas('hierarchical_dictionary', 2);
SELECT dictHas('hierarchical_dictionary', 7);

┌─dictHas('hie⋯ionary', 2)─┐
│                        1 │
└──────────────────────────┘
┌─dictHas('hie⋯ionary', 7)─┐
│                        0 │
└──────────────────────────┘

dictIsIn

Introduced in: v1.1

Checks the ancestor of a key through the whole hierarchical chain in the dictionary.

Syntax

dictIsIn(dict_name, child_id_expr, ancestor_id_expr)

Arguments

• dict_name — Name of the dictionary. String
• child_id_expr — Key to be checked. String
• ancestor_id_expr — Alleged ancestor of the child_id_expr key. const String

Returned value

Returns 0 if child_id_expr is not a child of ancestor_id_expr, 1 if child_id_expr is a child of ancestor_id_expr or if child_id_expr is an ancestor_id_expr. UInt8

Examples

Check hierarchical relationship

-- valid hierarchy
SELECT dictIsIn('hierarchical_dictionary', 6, 3)

-- invalid hierarchy
SELECT dictIsIn('hierarchical_dictionary', 3, 5)

┌─dictIsIn('hi⋯ary', 6, 3)─┐
│                        1 │
└──────────────────────────┘
┌─dictIsIn('hi⋯ary', 3, 5)─┐
│                        0 │
└──────────────────────────┘