<1>select A.* from A, B WHERE A.ID=B.ID AND B.ZT=3
<2>select * FROM A WHERE A.ID IN (SELECT ID FROM B WHERE ZT=3)
<3>select A.* FROM A, (SELECT ID FROM B WHERE ZT=3) C WHERE A.ID=C.ID
<1>,<2>,<3>哪个效率高些呢?还能不能写出效率更高的而且功能不变的SQL语句?
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哪个效率高一些?
select A.* from A, B WHERE A.ID=B.ID AND B.ZT=3 select * FROM A WHERE A.ID IN (SELECT ID FROM B WHERE ZT=3) select A.* FROM A, (SELECT ID FROM B WHERE ZT=3) C WHERE A.ID=C.ID ,,哪个效率高些呢?还能不能写出效率更高的而且功能不变的SQL语句?