mysql - mysql别名的未知列问题

Question

当列是创建的别名时，我不明白为什么我会得到一个未知列。任何帮助都会很棒。

代码:

SELECT DISTINCT 
    c.id, 
    ((SUM(c.width_feet)*12)+(SUM(c.width_inches))) AS width, 
    ((SUM(c.height_feet)*12)+(SUM(c.height_inches))) AS height 
    FROM carpets AS c 
    WHERE c.active = '1' 
    AND (width BETWEEN '0' AND '275') 
    AND (height BETWEEN '0' AND '599') 
    ORDER BY c.item_no 

错误:

Unknown column 'width' in 'where clause'

Answer 1

您不能直接通过名称访问别名。

一种解决方案是在子查询中使用别名包装查询，然后在外部查询中引用别名:

SELECT DISTINCT * 
FROM 
    (
     SELECT c.id, 
          ((SUM(c.width_feet)*12)+(SUM(c.width_inches))) AS width, 
          ((SUM(c.height_feet)*12)+(SUM(c.height_inches))) AS height
     FROM carpets AS c 
     WHERE c.active = '1'
    ) sub
WHERE (sub.width BETWEEN '0' AND '275') 
AND   (sub.height BETWEEN '0' AND '599') 
ORDER BY sub.item_no