與子查詢更新表，並複製

Question

我需要基於另一個表更新表，所以我必須聲明：

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

，這讓我錯誤說：

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

我試過DISTINCT但狀態值也不同，所以DISTINCT不起作用。所以我也改變了它：

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

現在它不會給出錯誤。

問題是，如果子查詢返回null，它也將更新行並清除內容。任何修補程序？

Answer 1

可以確保只有用火柴行被更新如下：

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

合併變種（10克+）：

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;