SQL服務器 - 如何更新多列/條件，而忽略某些列WHERE語句

Question

我有兩個表，並希望在SQL Server 2008中更新表T：

表寬：

+--------+----+------+------+------+ 
| DataID | AFD| PSD | PFD | ASD |  
+--------+----+------+------+------+ 
|  1 | B | E | A |  | 
|  2 | I |  | B | W |  
|  3 | |  | Y | D | 
|  4 | | Q |  | T |  
|  5 | T | E | D | T | 
+--------+----+------+------+------+ 

表t：

+--------+----+------+------+------+ 
| DataID | AFD| PSD | PFD | ASD |  
+--------+----+------+------+------+ 
|  1 | A | E |  | Z | 
|  2 | B | F | Y |  |  
|  3 | C | G | G | T | 
|  4 | B | E |  |  |  
|  5 | T | G | Y | Z | 
+--------+----+------+------+------+ 

問題/嘗試：如何更新表t檢查多個條件？

注意：NULL是文本不是空列。

update t 
SET t.ACTFINISHDATE = GETDATE() 
,t.PROJSTARTDATE = 
(CASE 2 
WHEN t.PROJSTARTDATE = 'NULL' THEN t.PROJSTARTDATE = w.PROJSTARTDATE 
WHEN w.PROJSTARTDATE = 'NULL' THEN GETDATE() 
ELSE GETDATE() 
END) 
,t.PROJFINISHDATE = 
(CASE 3 
WHEN t.PROJFINISHDATE = 'NULL' THEN t.PROJFINISHDATE = w.PROJFINISHDATE 
WHEN w.PROJFINISHDATE = 'NULL' THEN GETDATE() 
ELSE GETDATE() 
END) 
,t.ACTSTARTDATE = 
(CASE 3 
WHEN t.ACTSTARTDATE = 'NULL' THEN t.ACTSTARTDATE = w.ACTSTARTDATE 
WHEN w.ACTSTARTDATE = 'NULL' THEN GETDATE() 
ELSE GETDATE() 
END) 

FROM w 
    JOIN t ON w.DataID = t.DataID 
WHERE ((cold IN ('A', 'B') 
     AND cols IN ('E', 'F')) 
     OR (cold = 'C' 
      AND cols = 'G')) 

問題2：如何忽略更新上的cols在寒冷和F數據C數據（所以基本上，忽略任何數據，其中冷= C和cols = F）

表筆與其他列：

+--------+-----+-------+ 
| DataID | Cold| ColS |  
+--------+-----+-------+ 
|  1 | A | E  | 
|  2 | B | G  |  
|  3 | A | G  | 
|  4 | B | E  | 
|  5 | C | F  | 
|  6 | C | F  | 
+--------+-----+-------+ 

Answer 1

假設你join工作，那麼如下的語句case應改爲：

update t 
set t.ACTFINISHDATE = GETDATE(), 
    t.PROJSTARTDATE = 
     CASE WHEN t.PROJSTARTDATE = 'NULL' THEN w.PROJSTARTDATE 
     ELSE GETDATE() 
     END, 
    t.PROJFINISHDATE = 
     CASE WHEN t.PROJFINISHDATE = 'NULL' THEN w.PROJFINISHDATE 
     ELSE GETDATE() 
     END, 
    t.ACTSTARTDATE = 
     CASE WHEN t.ACTSTARTDATE = 'NULL' THEN w.ACTSTARTDATE 
     ELSE GETDATE() 
     END 
FROM w 
    LEFT JOIN T ON.. 
WHERE .... 

你沒有看到很多的更新outer joins雖然...

Answer 2

假設值是NULL，而不是'NULL'作爲例子，你可以這樣做：

update t 
SET t.ACTFINISHDATE = GETDATE() 
    ,t.PROJSTARTDATE = COALESCE(t.PROJSTARTDATE, w.PROJSTARTDATE, GETDATE()) 
    ,t.PROJFINISHDATE = COALESCE(t.PROJFINISHDATE, w.PROJFINISHDATE, GETDATE()) 
    ,t.ACTSTARTDATE = COALESCE(t.ACTSTARTDATE, w.ACTSTARTDATE, GETDATE()) 
....