mysql - WHERE 子句中的列别名

Question

问题

我在查询中使用备用列名(别名)，我可以将别名“given_name”用作 ORDER BY 的一部分，但无法将其用作 WHERE 子句的一部分。 WHERE“given_name”是作为我无法控制的请求的结果传入的，我不知道应该在 WHERE 条件中使用的实际列名。

问题

1. 有没有办法/技巧在 WHERE 子句中使用列别名？
2. 有没有办法从别名中找到列名？

研究

经过一些研究，看起来好像在 WHERE 子句之后添加了别名。

例子

SELECT profile.id AS id, given.name AS 'given_name', family.name AS 'family_name'
FROM green_profile profile 
LEFT JOIN green_name given ON given.profileid = profile.id AND given.name_typeid = 0 
LEFT JOIN green_name family ON family.profileid = profile.id AND family.name_typeid = 1 
WHERE given_name LIKE 'levi%' 
ORDER BY given_name DESC LIMIT 0 , 25

Answer 1

未经测试，但这个 hack 应该有效......

SELECT * FROM (  
    SELECT profile.id AS id, given.name AS 'given_name', family.name AS 'family_name'
    FROM green_profile profile 
    LEFT JOIN green_name given ON given.profileid = profile.id AND given.name_typeid = 0 
    LEFT JOIN green_name family ON family.profileid = profile.id AND family.name_typeid = 1   
) as temptable
WHERE given_name LIKE 'levi%' 
ORDER BY given_name DESC LIMIT 0 , 25

它的工作原理是从您的原始 select 语句(没有 where 子句和排序)简单地创建一个临时表，该表具有您指定的列名。然后，您可以从中选择所需的列名。

更好的方法可能是创建一个 View ，其中包含您想要的列名，然后从 View 中选择...

CREATE VIEW newtable AS
SELECT profile.id AS id, given.name AS 'given_name', family.name AS 'family_name'
FROM green_profile profile 
LEFT JOIN green_name given ON given.profileid = profile.id AND given.name_typeid = 0 
LEFT JOIN green_name family ON family.profileid = profile.id AND family.name_typeid = 1;

然后……

SELECT * FROM newtable
WHERE given_name LIKE 'levi%' 
ORDER BY given_name DESC LIMIT 0 , 25