Question

我需要根据另一个表更新表，所以我有声明：

update FAULTS
set FAULTS.FAULT_STATE = (
    select INCIDENTS.TICKET_STATE from INCIDENTS
    where INCIDENTS.CF_ID = FAULTS.CF_ID
)

它给我错误的说法：

ORA-01427: single-row subquery returns more than one row

我尝试过DISTINCT，但状态值也不同，所以DISTINCT不起作用。所以我也改了它：

update FAULTS
set FAULTS.FAULT_STATE = (
    select INCIDENTS.TICKET_STATE from INCIDENTS
    where INCIDENTS.CF_ID = FAULTS.CF_ID and rownum = 1
)

现在它不会出错。

问题是，如果子查询返回null，它还将更新行并清除内容。对此有何解决方法？

Answer 1

您可以确保只有匹配的行才会更新如下：

update FAULTS
set FAULTS.FAULT_STATE = (
    select INCIDENTS.TICKET_STATE from INCIDENTS
    where INCIDENTS.CF_ID = FAULTS.CF_ID and rownum = 1
)
where exists (
    select INCIDENTS.TICKET_STATE from INCIDENTS
    where INCIDENTS.CF_ID = FAULTS.CF_ID
)

Answer 2

合并变体（10g +）：

merge into faults
using (select cf_id, ticket_state from incidents) incidents
   on (incidents.cf_id = faults.cf_id)
when matched then update
 set fault_state=ticket_state;

使用子查询和重复更新表

2 个答案: