-- INSELECT    T1.*FROM    role_menu T1WHERE    T1.ROLEUUID IN (        SELECT            T2.uuid        FROM            role T2        WHERE            T2.UUID = '1'    );-- EXISTS SELECT    T1.*FROM    role_menu t1WHERE    EXISTS (        SELECT            T2.*        FROM            role T2        WHERE            t1.ROLEUUID = T2.uuid        AND t2.uuid = '1'    );

IN 是结果集中删选数据

EXISTS 是判断是否存在

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两三个条件使用or

多个使用IN

数据量大使用EXISTS

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