SELECT T1.A,T1.B,(SELECT C FROM T2 WHERE T2.A=T1.A AND T2.B=T1.B) C,(SELECT C FROM T3 WHERE T3.A=T1.A AND T3.B=T1.B) D,(SELECT C FROM T4 WHERE T4.A=T1.A AND T4.B=T1.B) E FROM T1表中有几千万条数据这样查询的效率是不是很低啊，修改下边的会不会好点呢。
SELECT T1.A,T1.B,T2.C,T3.D,T4.E FROM T1,T1,T3,T4,T5
WHERE T1.A=T2.A(+) AND T1.B=T2.B(+) AND T1.A=T3.A(+) AND T1.B=T3.B(+) AND T1.A=T3.A(+) AND T1.B=T3.B(+)
AND T1.A=T4.A AND T1.B=T4.B
这两种哪个好点呢
SELECT T1.A,T1.B,T2.C,T3.D,T4.E FROM T1,T1,T3,T4,T5
WHERE T1.A=T2.A(+) AND T1.B=T2.B(+) AND T1.A=T3.A(+) AND T1.B=T3.B(+) AND T1.A=T3.A(+) AND T1.B=T3.B(+)
AND T1.A=T4.A AND T1.B=T4.B
这两种哪个好点呢
解决方案 »
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