Mysql SELECT优先级

Question

我的数据库缺少一些值:

Name   Surname    Country   Salary

John   Walker     USA       800
       Walker     Canada    1000
Peter  Walker     Canada    800
John   Walker               900
Peter  Farmer     USA       1200
...    ...        ...

我想SELECT Name和Surname and Country,如果没有值,我想按名称和国家选择SELECT,如果没有值,我想按Surname和Country选择.

我现在在使用:

SELECT Salary FROM table_name
WHERE (Name='InputFromPHP' AND Surname='InputFromPHP' AND Country='InputFromPHP')
OR (Name='InputFromPHP' AND Surname='InputFromPHP')
OR (Name='InputFromPHP' AND Country='InputFromPHP')

我想优先考虑,所以它会精确选择什么是输入PHP,但是当数据库中有多个值时,它会产生SQL错误.

提前一百万谢谢.

Answer 1

你可以使用order by和limit:

SELECT   Salary 
FROM     table_name
WHERE    Name='InputFromPHP'
  AND    (Surname='InputFromPHP' OR Country='InputFromPHP')
ORDER BY CASE Surname WHEN 'InputFromPHP' THEN 0 ELSE 1 END, 
         CASE Country WHEN 'InputFromPHP' THEN 0 ELSE 1 END
LIMIT    1  

请注意,您的where子句始终是必需的Name='InputFromPHP',因此可以从该or子句中取出.