如何将 BigQuery 表架构导出为 DDL

Question

我需要使用与现有表相同的架构创建 BigQuery 表。在标准的 MySql 中有SHOW CREATE TABLE，BigQuery 有类似的东西吗？

Answer 1

SELECT
 table_name, ddl
FROM
 `bigquery-public-data`.census_bureau_usa.INFORMATION_SCHEMA.TABLES;

https://cloud.google.com/blog/topics/developers-practitioners/spring-forward-bigquery-user-friend-sql

Answer 2

没有类似于 MySQL 的 SHOW CREATE TABLE，但可以使用 UDF 生成数据集中表的 DDL 语句......

使用以下脚本并确保将“mydataset”替换为您的。你甚至可以添加一个 WHERE 谓词来只输出特定的表 DDL

复制所需表的输出并将其粘贴到新的 Compose Query 窗口中，并为其指定一个新表名！

CREATE TEMP FUNCTION MakePartitionByExpression(
  column_name STRING, data_type STRING
) AS (
  IF(
    column_name = '_PARTITIONTIME',
    'DATE(_PARTITIONTIME)',
    IF(
      data_type = 'TIMESTAMP',
      CONCAT('DATE(', column_name, ')'),
      column_name
    )
  )
);

CREATE TEMP FUNCTION MakePartitionByClause(
  columns ARRAY<STRUCT<column_name STRING, data_type STRING, is_nullable STRING,  is_partitioning_column STRING, clustering_ordinal_position INT64>>
) AS (
  IFNULL(
    CONCAT(
      'PARTITION BY ',
      (SELECT MakePartitionByExpression(column_name, data_type)
       FROM UNNEST(columns) WHERE is_partitioning_column = 'YES'),
      '\n'),
    ''
  )
);

CREATE TEMP FUNCTION MakeClusterByClause(
  columns ARRAY<STRUCT<column_name STRING, data_type STRING, is_nullable STRING,  is_partitioning_column STRING, clustering_ordinal_position INT64>>
) AS (
  IFNULL(
    CONCAT(
      'CLUSTER BY ',
      (SELECT STRING_AGG(column_name, ', ' ORDER BY clustering_ordinal_position)
        FROM UNNEST(columns) WHERE clustering_ordinal_position IS NOT NULL),
      '\n'
    ),
    ''
  )
);

CREATE TEMP FUNCTION MakeNullable(data_type STRING, is_nullable STRING)
AS (
  IF(not STARTS_WITH(data_type, 'ARRAY<') and is_nullable = 'NO', ' NOT NULL', '')
);

CREATE TEMP FUNCTION MakeColumnList(
  columns ARRAY<STRUCT<column_name STRING, data_type STRING, is_nullable STRING,  is_partitioning_column STRING, clustering_ordinal_position INT64>>
) AS (
  IFNULL(
    CONCAT(
      '(\n',
      (SELECT STRING_AGG(CONCAT('  ', column_name, ' ', data_type,  MakeNullable(data_type, is_nullable)), ',\n')
       FROM UNNEST(columns)),
      '\n)\n'
    ),
    ''
  )
);

CREATE TEMP FUNCTION MakeOptionList(
  options ARRAY<STRUCT<option_name STRING, option_value STRING>>
) AS (
  IFNULL(
    CONCAT(
      'OPTIONS (\n',
      (SELECT STRING_AGG(CONCAT('  ', option_name, '=', option_value), ',\n') FROM UNNEST(options)),
      '\n)\n'),
    ''
  )
);

WITH Components AS (
  SELECT
    CONCAT('`', table_catalog, '.', table_schema, '.', table_name, '`') AS table_name,
    ARRAY_AGG(
      STRUCT(column_name, data_type, is_nullable, is_partitioning_column, clustering_ordinal_position)
      ORDER BY ordinal_position
    ) AS columns,
    (SELECT ARRAY_AGG(STRUCT(option_name, option_value))
     FROM mydataset.INFORMATION_SCHEMA.TABLE_OPTIONS AS t2
     WHERE t.table_name = t2.table_name) AS options
  FROM mydataset.INFORMATION_SCHEMA.TABLES AS t
  LEFT JOIN mydataset.INFORMATION_SCHEMA.COLUMNS
  USING (table_catalog, table_schema, table_name)
  WHERE table_type = 'BASE TABLE'
  GROUP BY table_catalog, table_schema, t.table_name
)
SELECT
  CONCAT(
    'CREATE OR REPLACE TABLE ',
    table_name,
    '\n',
    MakeColumnList(columns),
    MakePartitionByClause(columns),
    MakeClusterByClause(columns),
    MakeOptionList(options))
FROM Components

有关更多信息，请检查 -> 使用 INFORMATION_SCHEMA https://cloud.google.com/bigquery/docs/information-schema-tables获取表元数据