oracle資料庫中有乙個表formtable_main_159_dt1結構如下
mainid,id
161,100,
161,101,
161,102,
162,103
162,104
163,105
現在增加乙個字段序號，實現如下的效果
mainid,id，xuhao
161,100,1
161,101,2
161,102,3
162,103,4
162,104,5
163,105,6
先使用如下語句實現出效果。
select row_number() over(partition by mainid order by id ) as xh,id,mainid from formtable_main_159_dt1
然後用update語句去更新新增欄位中的值；
最先用：update t1 set t1.c1=(select c2 from t2 where t1.id=t2.id) where exists （select 1 from t2 where t2.id=t1.id）
update formtable_main_159_dt1 set xuhao=(select xuhao from (select row_number() over(partition by mainid order by id ) as xuhao ,id from formtable_main_159_dt1) a1 where formtable_main_159_dt1.id=a1.id)
where
exists(select 1 from formtable_main_159_dt1,(select row_number() over(partition by mainid order by id ) as xuhao ,id from formtable_main_159_dt1) a1 where formtable_main_159_dt1.id=a1.id)
執行時間很長，而且語句寫的感覺及其囉嗦。
於是換一種寫法:update (select t1.c1,t2.c2 from t1,t2 where t1.id=t2.id) t set c1=c2
update ( select a1.xuhao , a2.xh from formtable_main_159_dt1 a1,(select row_number() over(partition by mainid order by id ) as xh,id from formtable_main_159_dt1) a2 where a1.id=a2.id ) t set xuhao=xh
於是再換一種寫法：
update ( select xuhao, row_number() over(partition by mainid order by id ) as xh from formtable_main_159_dt1) t set xuhao=xh
結果又是提示錯誤： ora-01732: 此檢視的資料操縱操作非法
原來這種update寫法需要主鍵的。
再換寫法：merge into t1 using (select t2.c2,t2.id from t2) t on (t.id=t1.id) when matched then update set t1.c1=t.c2
merge into formtable_main_159_dt1 a1 using (select row_number() over(partition by mainid order by id ) as xh,id,mainid from formtable_main_159_dt1) a2 on (a1.id=a2.id)
when matched then update
set a1.xuhao=a2.xh
現在好了，執行很快。
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