兩SQL語句比較
各位，請幫個忙~~ 下面兩條語句請問有什麼差異呢？請問可以寫出與“語句一”等價的表達式嗎？謝謝。
語句一：
SELECT DISTINCT CNAME
FROM COURSES C WHERE '男 '=all (select sex from enrolls,students where enrolls.sno=students.sno and enrolls.cno=C.cno)
語句二：
select distinct cname from courses,students,enrolls where students.sno=enrolls.sno and courses.cno=enrolls.cno and students.sex= '男 '
[解决办法]
-------- =all -------
SELECT DISTINCT CNAME
FROM COURSES C WHERE '男 ' in (select sex from enrolls,students where enrolls.sno=students.sno and enrolls.cno=C.cno)
[解决办法]
就是ALL的使用区别
