Oracle中的條件更新聲明

Question

我在Oracle中構建條件更新語句時遇到問題。對於易懂，我會簡化問題，基本上我的更新語句應該是這樣的：

UPDATE SAMPLE_TAB1 t 
    SET t.sample_column1 =NVL(t.sample_column1, **SOME LOGIC**); 

的***SOME LOGIC***部分應該是這樣的：（請考慮這只是一個僞代碼）

IF ((SELECT sample_column2 FROM SAMPLE_TAB2 
     WHERE sample_column2= sample_value2 
     AND sample_column3 = sample_value3)='FALSE' THEN 
    t.sample_column1 =0; 
ELSE 

    t.sample_column1 =(SELECT sample_column1 FROM SAMPLE_TAB3 
         WHERE sample_column4= sample_value4 
         AND sample_column5 = sample_value5) 

END IF; 

任何關於這個問題的想法都會受到歡迎。謝謝。

Answer 1

試試下面的代碼

UPDATE SAMPLE_TAB1 t 
    SET t.sample_column1 = (
     case when ((SELECT sample_column2 FROM SAMPLE_TAB2 
          WHERE sample_column2= sample_value2 
          AND sample_column3 = sample_value3) = 'FALSE') 
      then 0 
     else 
      (SELECT sample_column1 FROM SAMPLE_TAB3 
         WHERE sample_column4= sample_value4 
         AND sample_column5 = sample_value5) 
     end 

    ) 
    WHERE t.sample_column1 is not null; 

Answer 2

嘗試以下

UPDATE SAMPLE_TAB1 t 
    SET t.sample_column1 = NVL((SELECT sample_column2 FROM ...), 0) 
WHERE t.sample_column1 is not null 
;