表A,假设字段名有ID、NAME,ID是索引表B,假设字段名有ID、NAME,此表无索引。问题:1、select id from A where left(id,3)=‘123’,是否会用到索引?2、select * from A join B on A.id=B.id,是否会用到索引?3、select * from A join B on A.name=B.name and left(A.id,3)='123',是否...
显示全部表A,假设字段名有ID、NAME,ID是索引
表B,假设字段名有ID、NAME,此表无索引。
问题:
1、select id from A where left(id,3)=‘123’,是否会用到索引?
2、select * from A join B on A.id=B.id,是否会用到索引?
3、select * from A join B on A.name=B.name and left(A.id,3)='123',是否会用到索引?
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