左连接 - 未知列错误1054

Question

我不断收到＃1054 - 'where子句'中的未知列'color'。

我的查询的简化版本如下。

SELECT *, "red" AS colour 
FROM (
    SELECT *,'calls' AS 'tbl', id AS cid FROM calls) as c 
WHERE colour='red' 
ORDER BY colour ASC, c.created_date DESC 

如果我删除WHERE行，查询执行得很好，颜色被识别并且一切正常。

任何帮助，将不胜感激。

Answer 1

这是因为你不能在你的WHERE和ORDER BY子句中使用别名

所以，你将不得不做一些像

SELECT *, IF(c.status = '1', "green", "red") AS colour 
FROM (
    SELECT *,'calls1' AS 'tbl', id AS cid FROM calls1 
    WHERE uid LIKE '%1111%' 
    ORDER BY timestamp DESC 
    UNION 
    SELECT *,'calls2' AS 'tbl', id AS cid FROM calls2 
    WHERE uid LIKE '%1111%' 
    ORDER BY timestamp DESC 
) as c 
LEFT JOIN objects AS o ON o.call_id = c.id 
WHERE c.status = 'the color id you want' // or you can rewrite your if here 
ORDER BY c.status ASC, c.timestamp DESC 

或者，这为您简化查询

SELECT *, "red" AS colour 
FROM (
    SELECT *,'calls' AS 'tbl', id AS cid FROM calls) as c 
WHERE c.status = 'the color id you want' 
ORDER BY c.created_date DESC 

为什么按颜色分类，如果它总是红色？

Answer 2

试试这个WHERE c.status !='1'

SELECT *, IF(c.status = '1', "green", "red") AS colour 
FROM (
    SELECT *,'calls1' AS 'tbl', id AS cid FROM calls1 
    WHERE uid LIKE '%1111%' 
    ORDER BY timestamp DESC 
    UNION 
    SELECT *,'calls2' AS 'tbl', id AS cid FROM calls2 
    WHERE uid LIKE '%1111%' 
    ORDER BY timestamp DESC 
) as c 
LEFT JOIN objects AS o ON o.call_id = c.id 
WHERE c.status != '1' 
ORDER BY colour ASC, c.timestamp DESC 

Answer 3

为您更新的问题，我认为你可以做别名

SELECT * FROM (
SELECT *, "red" AS colour 
FROM (
    SELECT *,'calls' AS 'tbl', id AS cid FROM calls) as c 
) as v 
WHERE colour='red' 
ORDER BY colour ASC, v.created_date DESC 

Answer 4

使用在where子句是不是一个好方法一栏。请参考以下链接。

http://dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html

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标准SQL不允许在WHERE子句中的列别名引用。这种限制是强加的，因为当WHERE子句被评估时，列值可能还没有被确定。例如，下面的查询是非法的：

SELECT id, COUNT(*) AS cnt FROM tbl_name WHERE cnt > 0 GROUP BY id; 

---

使用具有的别名或更改条件WHERE子句中使用精确的列名。