Netezza 是否不支持多个相关查询？

Question

这可能更容易用代码解释，所以我目前使用的是这样的东西：

'A' in
    (
        SELECT DISTINCT b.col1
        FROM table b
        WHERE b.ky1 = a.ky1
            AND b.ky2 = a.ky2
            AND b.group = a.group
            AND b.rowNum < a.rowNum
    )

在 where 子句中。本质上，我试图查看 A 是否是外部查询指定的行之前的任何点的值。这是独立工作的。问题是当我将以下内容添加到查询中时：

OR
'S' in
    (
        SELECT DISTINCT b.col1
        FROM tableb b
        WHERE b.ky1 = a.ky1
            AND b.ky2 = a.ky2
            AND b.group = a.group
            AND b.rowNum < a.rowNum
    )

现在，Netezza 生成以下错误消息：

ERROR:  (2) This form of correlated query is not supported - consider rewriting

我觉得解决这个问题的唯一方法是进行某种连接，但我不确定如何在不产生大量重复项的情况下进行连接。有什么建议吗？

Answer 1

从 7.2 版开始，Netezza 中的相关子查询具有以下使用注意事项，如文档所述here。

If you choose to use correlated subqueries, keep in mind the following restrictions on the form and placement of correlated subqueries:

You can use correlated subqueries in WHERE clauses.

You can use correlated subqueries in inner join conditions and with the equal join condition operator.

You can use correlated subqueries in mixed correlated expressions only in the following form:

expr(corr_columA, corr_columnB,...) = expr(local_columnX, local_columnY,...)

You cannot use correlated subqueries in SET operations (UNION, INTERSECT, EXCEPT, and MINUS).

You cannot use correlated subqueries in aggregates with GROUP BY and HAVING clauses.

You cannot use correlated subqueries in ORed clauses or in CASE/WHEN expressions. ^=== You are here

You cannot use correlated subqueries in IN lists.

You cannot use correlated subqueries in SELECT lists.

如果将 OR 更改为 AND，您会发现查询将运行。当然不是说它会产生你想要的结果。

您可以将其重写为 JOIN，但我需要先查看查询结构的平衡，然后才能试一试它可能是什么。

Netezza 是否不支持多个相关查询？

Are multiple correlated queries unsupported in Netezza?

sql

ansi-sql

netezza

correlated-subquery