我正在尝试将 3 个表连接在一起,但使用 IF 语句仅运行特定查询
我有一个用户表、客户表和员工表。下面的第一部分有效:
SELECT user.`userID`, `username`, `user`.email, `registeredBy`, `registeredDate`,
CONCAT(staff.firstName, ' ' ,staff.lastName) AS staffName FROM `user`
INNER JOIN `level` ON `user`.levelID = `level`.levelID
INNER JOIN `staff` ON `user`.registeredBy = `staff`.userID
我需要查看谁注册了显示正常的用户,但是如果用户级别为 2,我需要查看员工姓名,如果用户级别为 1,我需要查看客户姓名
INNER JOIN `staff` ON `user`.userID = staff.userID IF (user.level = 2)
INNER JOIN `customer` ON user.userID = customer.userID IF(user.level = 1)
添加上面的内容会产生错误
Not unique table/alias: 'staff'
如果我删除 staff 的 inner join,我就会得到错误
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IF(user.level = 2)' at line 6
我只需要根据级别显示客户姓名或员工姓名,但我无法理解,因为我正在加入员工表两次。一次获取注册用户的员工的成员,然后查看员工姓名(或客户)。
为了让事情变得更简单,我正在显示的页面示例是:
username | name | account type | registered by
希望我没有把它弄得太困惑而难以理解。
谢谢。
最佳答案
Select user.userID
, username
, user.email
, registeredBy, registeredDate
, Case
When User.Level = 2 Then Concat(Level2Staff.firstName, ' ' , Level2Staff.lastName)
When User.Level = 1 Then Concat(customer.firstName, ' ' , customer.lastName)
End
AS staffName
FROM user
Inner Join level
On user.levelID = level.levelID
Inner Join staff
On user.registeredBy = staff.UserID
Left Join customer
On customer.userID = user.UserID
And user.level = 1
Left Join staff As Level2Staff
On user.userID = Level2Staff.UserID
关于MYSQL Inner Join if 语句,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5585338/