左连接(外连接)sql语句
- WBOYOriginal
- 2016-06-07 17:46:573001browse
假设表的结构图为：
user_info表：
role_info表：
要从表user_info和表role_info中查询出某些数据，比如在登录系统时，
除了要以登录名和密码来查询信息外，还要查询额外的信息，比如用户的权限，那就可能用到连接。
这里用左连接：
sql语句如下：
select u.*,r.role_name,r.right_id from (SELECT * FROM user_info WHERE login_name=#login_name# AND password= #password# )AS u left outer join role_info r on u.role=r.role_code
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