MySQL中exists子查詢

概念 查詢返回的結果就只有0或者1,1表明成立,0表明不成立web 語法 where exists(查詢結果); where 1 : 永遠爲真svg 案例 求出有學生在的全部班級 select * from my_class as c where exists(select stu_id from my_student as s where c.class_id = s.class_id);

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