如果我从以下查询中删除exists语句,输出如何更改?
在oracle中存在vs不存在
UPDATE AR_CRDT C
set (OPERATOR_ID,UPDT_TS) = (SELECT AD.OPERATOR_ID,sysdate
FROM
(
Select A.*
FROM AR1_CUSTOMER_CREDIT A
)AD
WHERE AD.CREDIT_ID = C.CRDT_ID
)
where exists (SELECT 1
FROM
(
Select A.*
FROM AR1_CUSTOMER_CREDIT A
)AD
WHERE AD.CREDIT_ID = C.CRDT_ID
);
这类似于内连接和左外连接之间的区别。它实际上**是**内部连接和外部连接之间的区别,如果您将'update'重写为连接的更新,如下所述:http://stackoverflow.com/documentation/oracle/8061/update- with-joins#t = 201702151427027709587 – mathguy