Redshift SQL 以逗号分隔一个字段与一组两个字段

Question

我想用逗号分隔字段值和 GROUP BY Redshift 中的其他两个字段。

示例数据：

table_schema table_name column_name 
G1           G2         a
G1           G2         b
G1           G2         c
G1           G2         d
G3           G4         x
G3           G4         y
G3           G4         z

预期输出：

table_schema table_name column_name 
G1           G2         a, b, c, d
G3           G4         x, y, z

我可以在 MSSQL 中这样做：

SELECT table_schema, table_name, column_name = 
    STUFF((SELECT ', ' + column_name
           FROM your_table b 
           WHERE b.table_schema = a.table_schema AND b.table_name = a.table_name
          FOR XML PATH('')), 1, 2, '')
FROM information_schema.tables t
INNER JOIN information_schema.columns c on c.table_name = t.table_name AND c.table_schema = t.table_schema
GROUP BY table_schema, table_name

在 PostgreSQL 中这将是：

SELECT table_schema, table_name, String_agg(column_name, ',')
FROM information_schema.tables t
INNER JOIN information_schema.columns c on c.table_name = t.table_name AND c.table_schema = t.table_schema
GROUP BY table_schema, table_name

但是 Redshift 不包含 STRING_AGG 函数。

我不知道如何在 Redshift 中执行此操作。

编辑

SELECT CUST_ID,
       LISTAGG("ORDER", ', ')
WITHIN GROUP (ORDER BY "ORDER")
OVER (PARTITION BY CUST_ID) AS CUST_ID
FROM Table
ORDER BY CUST_ID

我的版本：

SELECT t.table_name, LISTAGG("column_name", ', ')
WITHIN GROUP (ORDER BY "column_name")
OVER (PARTITION BY t.table_name) AS table_schema
FROM information_schema.columns t
ORDER BY t.table_name

它给我以下错误：

0A000: Specified types or functions (one per INFO message) not supported on Redshift tables.

我不明白，我只是从一个节点中选择？

Answer 1

我认为 Redshift 不支持 listagg() 作为 window 函数。所以，可以在单独聚合后的结果中join：

SELECT t.CUST_ID, c.orders
FROM Table t JOIN
      (SELECT cust_id, LISTAGG("ORDER"::text, ', ')
WITHIN GROUP (ORDER BY "ORDER") as orders
       FROM table t
       GROUP BY cust_id
      ) c
      ON t.cust_id = c.cust_id
ORDER BY CUST_ID;

当然，我认为没有理由复制每一行的数据。聚合查询可能就足够了，因此结果集中每个客户只有一行。

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