Question

我有一个查询，我根据这样的数据创建一个字段：

SELECT 

id as ID, 
name as NAME, 
percent as PERCENT, 
hits AS HITS,
(30 * PERCENT) / 100 AS MAX_HITS_ALLOWED

FROM `table` 

WHERE MAX_HITS_ALLOWED > 10

我收到以下错误：

'where子句'
中的未知列'MAX_HITS_ALLOWED'

它必须是表中的一个字段，否则它不起作用？

Answer 1

MAX_HITS_ALLOWED是列别名，不能以这种方式使用。而是使用WHERE子句中的表达式。

SELECT 
    id as ID, 
    name as NAME, 
    percent as PERCENT, 
    hits AS HITS,
    (30 * PERCENT) / 100 AS MAX_HITS_ALLOWED
FROM `table` 
WHERE (30 * PERCENT) / 100 > 10

Answer 2

您无法在where中使用别名。请改用having子句：

SELECT 

id as ID, 
name as NAME, 
percent as PERCENT, 
hits AS HITS,
(30 * PERCENT) / 100 AS MAX_HITS_ALLOWED

FROM `table` 
having MAX_HITS_ALLOWED > 10

MySQL字段无法识别

2 个答案: