的BigQuery查詢查找表的列名

Question

我需要一個查詢找到BigQuery中的表格列的名稱，如下面的查詢在SQL：

SELECT column_name,data_type,data_length,data_precision,nullable FROM all_tab_cols where table_name ='EMP'; 

Answer 1

它目前無法檢索表的元數據（即列名和類型），但這不是第一次被請求。

是否有一個原因，你需要做這個查詢？表元數據可通過tables API獲取。

Answer 2

實際上，使用SQL可以這樣做。爲此，您需要查詢日誌記錄表以獲取正在創建的特定表的最後一個日誌。

例如，假設正裝表/每天創建：

CREATE TEMP FUNCTION jsonSchemaStringToArray(jsonSchema String) 
      RETURNS ARRAY<STRING> AS ((
      SELECT 
       SPLIT(
       REGEXP_REPLACE(REPLACE(LTRIM(jsonSchema,'{ '),'"fields": [',''), r'{[^{]+"name": "([^\"]+)"[^}]+}[, ]*', '\\1,') 
       ,',') 
     )); 
    WITH valid_schema_columns AS (
     WITH array_output aS (SELECT 
     jsonSchemaStringToArray(jsonSchema) AS column_names 
     FROM (
     SELECT 
      protoPayload.serviceData.jobInsertRequest.resource.jobConfiguration.load.schemaJson AS jsonSchema 
      , ROW_NUMBER() OVER (ORDER BY metadata.timestamp DESC) AS record_count 
     FROM `realself-main.bigquery_logging.cloudaudit_googleapis_com_data_access_20170101` 
     WHERE 
      protoPayload.serviceData.jobInsertRequest.resource.jobConfiguration.load.destinationTable.tableId = '<table_name>' 
      AND 
      protoPayload.serviceData.jobInsertRequest.resource.jobConfiguration.load.destinationTable.datasetId = '<schema_name>' 
      AND 
      protoPayload.serviceData.jobInsertRequest.resource.jobConfiguration.load.createDisposition = 'CREATE_IF_NEEDED' 
    ) AS t 
     WHERE 
     t.record_count = 1 -- grab the latest entry 
    ) 
     -- this is actually what UNNESTS the array into standard rows 
     SELECT 
     valid_column_name 
     FROM array_output 
     LEFT JOIN UNNEST(column_names) AS valid_column_name 

    )