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Question

我做這個SQL，我現在需要使用此查詢我需要更新T1表給出結果

SELECT DISTINCT t1.t1_val3, t1.t1_val4 
       DECODE (b_val, 
         'A', 'Its A', 
         'B', 'Its B', 
         'C', 'Its C', 
         NULL 
         ) decode_val, 

      FROM t1, t2, t3 
      WHERE t1.t1_val = t2.t2_val 
      AND t2.t2_val = t3.t3_val 
      AND t3.t3_val2 <> 'PSA' 
      AND t3.t3_val2 = 'Y' 

更新表。

這樣的事情，

update t1 
set 
t1.val5=decode_val 
where t1.t1_val3= value returned from above query(first column t1_val3) 
and t1.t1_val4= value returned from above query(2nd column t1_val4) 

DB - 10克

Answer 1

既然你是在10g中，MATCHED和NOT MATCHED條款現在optional是。

MERGE INTO t1 a 
USING (SELECT DISTINCT t1.t1_val3, t1.t1_val4 
       DECODE (b_val, 
         'A', 'Its A', 
         'B', 'Its B', 
         'C', 'Its C', 
         NULL 
         ) decode_val, 

      FROM t1, t2, t3 
      WHERE t1.t1_val = t2.t2_val 
      AND t2.t2_val = t3.t3_val 
      AND t3.t3_val2 <> 'PSA' 
      AND t3.t3_val2 = 'Y') b 
ON(a.t1_val3 = b.t1_val_3 and a.t1_val4 = b.t1_val4) 
WHEN MATCHED THEN 
    UPDATE SET a.t1.val5 = b.decode_val 

Answer 2

試試這個：

update t1 
set 
t1.val5 =DECODE (b_val, 
        'A', 'Its A', 
        'B', 'Its B', 
        'C', 'Its C', 
        NULL 
        ) 

     FROM t1, t2, t3 
     WHERE t1.t1_val = t2.t2_val 
     AND t2.t2_val = t3.t3_val 
     AND t3.t3_val2 <> 'PSA' 
     AND t3.t3_val2 = 'Y'