MINUS在MySQL中的運算符？

Question

我有一些表格，我收到的電子郵件。我不希望收到表tbl_unsubscribe中的電子郵件。我寫了這樣的查詢：

SELECT cand_email FROM tbl_cand_data 
UNION 
SELECT emp_email FROM tbl_emp_data 
UNION 
SELECT email FROM tbl_uptade_list 
UNION 
SELECT feed_email FROM tbl_feedback 
UNION 
SELECT admin_email FROM tbl_admin_emails  

但我得到一個語法錯誤。 MINUS運算符對MySQL無效嗎？

Answer 1

A NOT IN()子查詢可以在這裏使用，因爲MySQL不支持MINUS。

SELECT 
    cand_email 
FROM tbl_cand_data 
WHERE can_email NOT IN (SELECT un_email FROM tbl_unsubscribe) 

它也可以用LEFT JOIN做，尋找在un_email列空值：

SELECT cand_email 
FROM 
    tbl_cand_data 
    LEFT JOIN tbl_unsubscribe ON tbl_cand_data.can_email = tbl_unsubscribe.un_email 
WHERE tbl_unsubscribe.un_email IS NULL 

從一堆UNION操作中排除，包裹UNION組()爲子查詢：

SELECT email FROM (
    SELECT cand_email AS email FROM tbl_cand_data 
    UNION 
    SELECT emp_email AS email FROM tbl_emp_data 
    UNION 
    SELECT email FROM AS email tbl_uptade_list 
    UNION 
    SELECT feed_email AS email FROM tbl_feedback 
    UNION 
    SELECT admin_email AS email FROM tbl_admin_emails 
) email_list 
WHERE email NOT IN (SELECT un_email FROM tbl_unsubscribe) 

Answer 2

不幸的是，MySQL不支持MINUS和INTERSECT，但是你可以使用連接獲得相同的結果（用於減號;對於相交集）的

SELECT cand_email FROM tbl_cand_data 
LEFT JOIN tbl_unsubscribe ON (cand_email = un_email) 
WHERE un_email IS NULL