Question

我需要使用与现有模式相同的模式创建BigQuery表。在标准的MySql中，有SHOW CREATE TABLE，BigQuery是否有类似的东西？

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-friendly-sql

Answer 2

与MySQL的SHOW CREATE TABLE相似，但是可以通过使用UDF在数据集中生成表的DDL语句...

使用以下脚本，并确保将“ mydataset”替换为您的脚本。您甚至可以添加WHERE谓词以仅输出特定的表DDL

复制所需表的输出并将其粘贴到新的“撰写查询”窗口中，并为其指定新的表名！

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

Answer 3

...以与现有模式相同的模式创建BigQuery表

您可以在“技巧”下使用新表作为目标（技巧是在WHERE FALSE中使用，这使得下面的查询免费，在保留模式的情况下输出为0行）

#standardSQL
SELECT * 
FROM `project.dataset.existing_table`
WHERE FALSE

或者您可以在DAS的CTAS（CREATE TABLE AS SELECT）类型中使用以上语句

如何将BigQuery表架构导出为DDL

3 个答案: