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JSONColumns

输入输出别名
✔✔

描述​

提示

JSONColumns* 格式的输出首先输出 ClickHouse 字段名，随后给出该字段在表中每一行的内容；直观上看，相当于将数据向左旋转了 90 度。

在这种格式下，所有数据都表示为一个 JSON 对象。

注意

JSONColumns 格式会将所有数据缓冲在内存中，并一次性作为单个数据块输出，因此可能会导致较高的内存消耗。

使用示例​

插入数据​

使用包含以下数据的 JSON 文件，并将其命名为 football.json：

{
    "date": ["2022-04-30", "2022-04-30", "2022-04-30", "2022-05-02", "2022-05-02", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07"],
    "season": [2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021],
    "home_team": ["Sutton United", "Swindon Town", "Tranmere Rovers", "Port Vale", "Salford City", "Barrow", "Bradford City", "Bristol Rovers", "Exeter City", "Harrogate Town A.F.C.", "Hartlepool United", "Leyton Orient", "Mansfield Town", "Newport County", "Oldham Athletic", "Stevenage Borough", "Walsall"],
    "away_team": ["Bradford City", "Barrow", "Oldham Athletic", "Newport County", "Mansfield Town", "Northampton Town", "Carlisle United", "Scunthorpe United", "Port Vale", "Sutton United", "Colchester United", "Tranmere Rovers", "Forest Green Rovers", "Rochdale", "Crawley Town", "Salford City", "Swindon Town"],
    "home_team_goals": [1, 2, 2, 1, 2, 1, 2, 7, 0, 0, 0, 0, 2, 0, 3, 4, 0],
    "away_team_goals": [4, 1, 0, 2, 2, 3, 0, 0, 1, 2, 2, 1, 2, 2, 3, 2, 3]
}

插入数据：

INSERT INTO football FROM INFILE 'football.json' FORMAT JSONColumns;

读取数据​

使用 JSONColumns 格式来读取数据：

SELECT *
FROM football
FORMAT JSONColumns

输出将为 JSON 格式：

{
    "date": ["2022-04-30", "2022-04-30", "2022-04-30", "2022-05-02", "2022-05-02", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07", "2022-05-07"],
    "season": [2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021, 2021],
    "home_team": ["Sutton United", "Swindon Town", "Tranmere Rovers", "Port Vale", "Salford City", "Barrow", "Bradford City", "Bristol Rovers", "Exeter City", "Harrogate Town A.F.C.", "Hartlepool United", "Leyton Orient", "Mansfield Town", "Newport County", "Oldham Athletic", "Stevenage Borough", "Walsall"],
    "away_team": ["Bradford City", "Barrow", "Oldham Athletic", "Newport County", "Mansfield Town", "Northampton Town", "Carlisle United", "Scunthorpe United", "Port Vale", "Sutton United", "Colchester United", "Tranmere Rovers", "Forest Green Rovers", "Rochdale", "Crawley Town", "Salford City", "Swindon Town"],
    "home_team_goals": [1, 2, 2, 1, 2, 1, 2, 7, 0, 0, 0, 0, 2, 0, 3, 4, 0],
    "away_team_goals": [4, 1, 0, 2, 2, 3, 0, 0, 1, 2, 2, 1, 2, 2, 3, 2, 3]
}

格式设置​

在导入过程中，如果将 input_format_skip_unknown_fields 设置为 1，则名称未知的列会被跳过。 在数据块中不存在的列将用默认值填充（此处可以使用 input_format_defaults_for_omitted_fields 设置）。