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  • 连接查询

    mysql4.1可嵌套多个查询

    一、内连接查询

    (1)delect bookid ,borrowTime,backTime,ifbak,bookname,author,price 

    from tb_borrow,tb_bookinfo where tb_borrow.bookid=tb_bookinfo.id;

    二、子查询

    (1)带in或not in

    select id,bookname,author

    from tb_bookinfo where id in(select bookid from tb_borrow);

    (2)带比较运算符的子查询

    (1)select score from tb_grade where name='优秀';

    (2)select * from  tb_student

        where score >= (select score from tb_grade where name='优秀')

    (3)带exists   (not exists)

    使用exist是关键字,内层查询语句不返回查询记录,而是返回一个真假值。返回真时:外层查询语句继续查询,返回false:外层查询不做任何查询或查不出任何记录;

    select id,bookname,author,price from tb_bookinfo

    where exists (select * from tb_borrow where tb_borrow.bookid=tb_bookinfo.id);

    (4)any  或all

    列名  比较运算符   any(子查询)

    select * from tb_student1

    where score > any(select score from tb_student1 where classid=13);

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  • 原文地址:https://www.cnblogs.com/shanpao/p/7668562.html
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