TRUNC（日期）與甲骨文

Question

子查詢我有如下圖所示

IF (TRUNC(lv_d_itr) IN 
(SELECT next_day(TRUNC(to_date('01-01-17','dd-mm-yy'),'YYYY') + 14*(level-1), 'WED')+7 
FROM dual 
CONNECT BY level <= 26)) THEN 

，檢查在子查詢日期的IF條件爲什麼我會得到下面的錯誤？用法是錯誤的？

PLS-00405: subquery not allowed in this context 

什麼可能是替代解決方案？

Answer 1

您可以用不同的方式編輯這個，一個簡單的可以是這樣的：

declare 
    n number; 
begin 
    select count(1) 
    into n 
    from 
     (  
     SELECT next_day(TRUNC(to_date('01-01-17','dd-mm-yy'),'YYYY') + 14*(level-1), 'MER')+7 as x 
     FROM dual 
     CONNECT BY level <= 26 
     ) 
    where x = TRUNC(lv_d_itr); 
    if n > 0 
     then ... 
    end if; 
    ... 
end; 

Answer 2

不能使用在PL/SQL IF語句子查詢：

BEGIN 
    IF 'X' IN (SELECT DUMMY FROM DUAL) THEN 
    DBMS_OUTPUT.PUT_LINE('X'); 
    END IF; 
END; 
/

威爾錯誤與PLS-00405: subquery not allowed in this context

您可以重構它以獲得相同的效果：

DECLARE 
    p_exists NUMBER; 
BEGIN 
    SELECT CASE WHEN 'X' IN (SELECT DUMMY FROM DUAL) 
       THEN 1 
       ELSE 0 
     END 
    INTO p_exists 
    FROM DUAL; 

    IF p_exists = 1 THEN 
    DBMS_OUTPUT.PUT_LINE('X'); 
    END IF; 
END; 
/