php mysql 连接运算符_php – MINUS运算符在MySQL？
在这里可以使用NOT IN()子查询,因为MySQL不支持MINUS.
SELECT
cand_email
FROM tbl_cand_data
WHERE can_email NOT IN (SELECT un_email FROM tbl_unsubscribe)
还可以使用LEFT JOIN,在un_email列中查找NULL：
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
要将它们从一系列UNION操作中排除,请将UNION组作为子查询包含在()中：
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)