mysql 1111无效使用组功能

Question

此查询工作正常：

SELECT leads.contact_id, count(leads.contact_id) as orders 
FROM leads
WHERE leads.status="sold" 
GROUP BY leads.contact_id    

但是这个没有。为什么？

SELECT leads.contact_id, count(leads.contact_id) as orders
FROM leads
WHERE orders > 1 and leads.status="sold" 
GROUP BY leads.contact_id    

执行此查询时出现错误

  

1054-“ where子句”中的未知列“ orders”

即使用计数（leads.contact_id）替换订单，它也不起作用：

SELECT leads.contact_id, count(leads.contact_id) as orders
FROM leads
WHERE count(leads.contact_id) > 1 and leads.status="sold" 
GROUP BY leads.contact_id 

返回以下错误消息：

  

1111-无效使用组功能

Answer 1

如果您了解SQL的操作顺序，您将知道为什么查询不起作用。

FROM clause
WHERE clause
GROUP BY clause
HAVING clause
SELECT clause
ORDER BY clause

WHERE子句在SELECT和GROUP BY之前进行评估。因此它将不知道count(leads.contact_id)或orders是什么。另一方面是HAVING之后的GROUP BY。用于过滤聚合。

SELECT leads.contact_id, count(leads.contact_id) as orders 
FROM leads
WHERE leads.status="sold" 
GROUP BY leads.contact_id  
HAVING orders > 1

Answer 2

我应该使用 HAVING 而不是 WHERE ，因为WHERE仅可用于过滤原始数据表，而不能用于过滤计算出的数据表。但是列 count（leads.contact_id）或 orders 是计算列，而不是表的原始列，因此我必须像这样使用HAVING才能使其工作： / p>

SELECT leads.contact_id, count(leads.contact_id) as orders 
FROM leads
WHERE leads.status="sold" 
GROUP BY leads.contact_id  
HAVING orders>1

也请参见此detailed explanation