通過自連接進行的Sybase SQL更新

Question

Sybase SQL中使用自連接進行更新的正確語法是什麼？例如。假設你有下面的表格（#tmptbl）：

account | client |amount | date 
------------------------------------- 
ACT1 | CLIENTA | 12 |2010-12-30 
ACT2 | CLIENTB | 5  |2010-12-30 
ACT1 | CLIENTA | 17 |2010-12-31 
ACT2 | CLIENTB | 6  |2010-12-31 

我想覆蓋2010-12-31金額從2010-12-30的金額。

我覺得寫東西是這樣的：

update old 
set old.amount = new.amount 
from #tmptbl old, #tmptbl new 
where 
/*filter old*/ 
old.account = 'ACT1' 
and old.date = '2010-12-30' 
and old.client = 'CLIENTA' 
/* self-join new and old*/ 
and old.account = new.account 
and old.client = new.client 
/* filter new */ 
and new.date = '2010-12-31' 

但它看起來並不像的Sybase接受「更新<>」子句中的別名。這樣做的正確方法是什麼？

謝謝！

Answer 1

這工作：

update #tmptbl 
set old.amount = new.amount 
from #tmptbl old, #tmptbl new 
where 
/*filter old*/ 
old.account = 'ACT1' 
and old.date = '2010-12-30' 
and old.client = 'CLIENTA' 
/* self-join new and old*/ 
and old.account = new.account 
and old.client = new.client 
/* filter new */ 
and new.date = '2010-12-31' 
go 

如果你離開了表的別名，你正在更新，即set amount = new.amount那麼的Sybase關聯你與更新表首先在from子句中使用匹配表，所以在這種情況下，爲了使更新工作，您需要從中讀取from #tmptbl new, #tmptbl old。

輸出：

account  client  amount  date    
---------- --------- --------- ---------------- 
ACT1  CLIENTA 12   30/12/2010 00:00 
ACT2  CLIENTB 5   30/12/2010 00:00 
ACT2  CLIENTB 6   31/12/2010 00:00 
ACT1  CLIENTA 12   31/12/2010 00:00 

Answer 2

你試過

update #tmptbl 
set amount = new.amount 
from #tmptbl old, #tmptbl new 
where 
/*filter old*/ 
old.account = 'ACT1' 
and old.date = '2010-12-30' 
and old.client = 'CLIENTA' 
/* self-join new and old*/ 
and old.account = new.account 
and old.client = new.client 
/* filter new */ 
and new.date = '2010-12-31'