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 程式師世界 >> 數據庫知識 >> MYSQL數據庫 >> MySQL綜合教程 >> MySQL不支撐INTERSECT和MINUS及其替換辦法

MySQL不支撐INTERSECT和MINUS及其替換辦法

編輯:MySQL綜合教程

MySQL不支撐INTERSECT和MINUS及其替換辦法。本站提示廣大學習愛好者:(MySQL不支撐INTERSECT和MINUS及其替換辦法)文章只能為提供參考,不一定能成為您想要的結果。以下是MySQL不支撐INTERSECT和MINUS及其替換辦法正文


Doing INTERSECT and MINUS in MySQL

Doing an INTERSECT

An INTERSECT is simply an inner join where we compare the tuples of one table with those of the other, and select those that appear in both while weeding out duplicates. So


SELECT member_id, name FROM a
INTERSECT
SELECT member_id, name FROM b


can simply be rewritten to


SELECT a.member_id, a.name
FROM a INNER JOIN b
USING (member_id, name)


Performing a MINUS
To transform the statement


SELECT member_id, name FROM a
MINUS
SELECT member_id, name FROM b


into something that MySQL can process, we can utilize subqueries (available from MySQL 4.1 onward). The easy-to-understand transformation is:


SELECT DISTINCT member_id, name
FROM a
WHERE (member_id, name) NOT IN
(SELECT member_id, name FROM table2);


Of course, to any long-time MySQL user, this is immediately obvious as the classical use-left-join-to-find-what-isn't-in-the-other-table:


SELECT DISTINCT a.member_id, a.name
FROM a LEFT JOIN b USING (member_id, name)
WHERE b.member_id IS NULL
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