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  • mysql_连表查询

    1.内连接(只取两张表的共同部分)

    # 将表employee 和 department 的相同部分根据employee表中的dep_id字段和department表中的id字段连接起来。
    select * from employee inner join department on employee.dep_id = department.id;

    2.左连接(在内连接的基础上保留左边表的记录)

    select * from employee left join department on employee.dep_id = department.id;

    3.右连接(在内连接的基础上保留右边表的记录)

    select * from employee right join department on employee.dep_id = department.id;

    4.全外连接(保留左右两表没有对应关系的记录)

    # 将左连接和右连接查出来的记录和在一起,再去重~
    select * from employee left join department on employee.dep_id = department.id union select * from employee right join department on employee.dep_id = department.id;

    #示例1:以内连接的方式查询employee和department表,并且employee表中的age字段值必须大于25,即找出年龄大于25岁的员工以及员工所在的部门
    select employee.name,department.name from employee inner join department on employee.dep_id = department.id where age > 25;
    
    #示例2:以内连接的方式查询employee和department表,并且以age字段的升序方式显示
    select * from employee inner join department on employee.dep_id = department.id order by age asc;
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  • 原文地址:https://www.cnblogs.com/wangdianchao/p/12271081.html
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