MySQL不支持INTERSECT和MINUS及其替代方法_MySQL

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MySQL不支持INTERSECT和MINUS及其替代方法

 

Doing INTERSECT and MINUS in MySQL Doing an INTERSECTAn 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. SoSELECT member_id, name FROM aINTERSECTSELECT member_id, name FROM bcan simply be rewritten toSELECT a.member_id, a.nameFROM a INNER JOIN bUSING (member_id, name)Performing a MINUSTo transform the statementSELECT member_id, name FROM aMINUSSELECT member_id, name FROM binto 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, nameFROM aWHERE (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.nameFROM a LEFT JOIN b USING (member_id, name)WHERE b.member_id IS NULL

 

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