Question

以下嵌套DB2 SQL查询无效。这嵌套了DELETE和WITH语句

delete from ADDRESS 
where 
    ADDRESS_ID in (with     addr (ADDRESS_ID) as (select a.ADDRESS_ID from ADDRESS a where a.MEMBER_ID between 50000000 and 999999999 and a.STATUS='T' and a.LASTCREATE < (current timestamp - 42 days)), 
                addrorder (ADDRESS_ID) as ( select ad.ADDRESS_ID from ADDR ad LEFT OUTER JOIN ORDERS o on o.ADDRESS_ID = ad.ADDRESS_ID where o.ADDRESS_ID is null), 
                addordi (ADDRESS_ID) as ( select ao.ADDRESS_ID from ADDRORDER ao LEFT OUTER JOIN ORDERITEMS oi on oi.ADDRESS_ID=ao.ADDRESS_ID where oi.ADDRESS_ID is null), 
                addordia (ADDRESS_ID) as ( select aoi.ADDRESS_ID from ADDORDI aoi LEFT OUTER JOIN ORDERITEMS oi ON oi.ALLOCADDRESS_ID=aoi.ADDRESS_ID where oi.ALLOCADDRESS_ID is null)
                select distinct aoia.ADDRESS_ID from ADDORDIA aoia LEFT OUTER JOIN HD_MEMBER_SUBSCR ms ON ms.ADDRESS_ID=aoia.ADDRESS_ID where ms.ADDRESS_ID is null fetch first 800000 rows only for read only with ur);

Answer 1

使用最简单的解决方案：您的查询不需要任何CTE。一般来说，在

时使用CTE

你试图抽象出一些连接/操作集（即通常作为视图创建）
您计划多次引用结果

（有一个相关的命名聚合结果集，但可以使用连接的子查询来完成）

对于简单的条件，请不要打扰。以下几乎应该在每个版本的DB2中运行（并且禁止FETCH FIRST，几乎每个RDBMS）：

DELETE FROM Address 
WHERE member_id >= 50000000 
      AND member_id < 1000000000
      AND status = 'T'
      AND lastCreate < CURRENT_TIMESTAMP - 42 DAYS
      AND NOT EXISTS (SELECT '1'
                      FROM Orders
                      WHERE Orders.address_id = Address.address_id)
      AND NOT EXISTS (SELECT '1'
                      FROM OrderItems
                      WHERE OrderItems.addressId = Address.address_id
                            OR OrderIterms.allocAddress_id = Address.address_id)
      AND NOT EXISTS (SELECT '1'
                      FROM HD_Member_Subscr
                      WHERE HD_Member_Subscr.address_id = Address.address_id)
FETCH FIRST 800000 ROWS ONLY
WITH UR

（实际上，我想知道FOR READ ONLY是否是问题的一部分。请注意，如果没有ORDER BY子句，行的顺序将是随机的 - 尽管可能address_id ）。

请注意，我已将BETWEEN替换为独占范围（我个人认为应该弃用BETWEEN，并且出于一致性原因，提倡为偶数整数范围明确定义范围。）

Answer 2

我同意@ Clockwork-Muse你在这里并不真正需要CTE，我认为DB2不支持具有DELETE语句的CTE（至少在LUW上）。

由于您说NOT EXISTS子句的性能不佳，您可以尝试使用LEFT JOIN s替代，但我不确定它会好得多。以下逻辑假定除了地址字段之外的表中的地址字段是用NOT NULL定义的，如果不是这样的话

如果你真的删除了足够的条目，要求你一次要做八十万个条目，那么你可能有很多数据，无论你如何处理它都会相当慢。

另外，为什么你有WITH UR？你真的想删除未提交的行吗？

DELETE FROM Address 
WHERE member_id >= 50000000 
  AND member_id < 1000000000
  AND status = 'T'
  AND lastCreate < CURRENT_TIMESTAMP - 42 DAYS

  AND address_id IN (
    SELECT address_id FROM (
        SELECT
             A.address_ID
            ,ROW_NUMBER() OVER () AS RN
        FROM Address     A
        LEFT JOIN Orders O
          ON O.address_id = A.address_id
        LEFT JOIN OrderItems OI
          ON OI.addressId = A.address_id
        LEFT JOIN OrderItems OI2
          ON OI2.allocAddress_id = A.address_id
        LEFT JOIN HD_Member_Subscr H
          ON H.address_id= A.address_id
        WHERE O.addressId         IS NULL
          AND OI.addressId        IS NULL
          AND OI2.allocAddress_id IS NULL
          AND H.address_id        IS NULL
    ) T1
    WHERE RN <= 800000
  )

DB2 delete和with statement

2 个答案: