mysql 1111無效使用組功能

Question

此查詢工作正常：

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

但這不是。 為什么？

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

執行此查詢時出現錯誤

1054-“ where子句”中的未知列“ orders”

即使用count（leads.contact_id）替換訂單也不起作用：

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 

返回以下錯誤消息：

1111-無效使用組功能

Answer 1

如果您了解SQL的操作順序，您將知道為什么查詢不起作用。

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

在SELECT和GROUP BY之前先評估WHERE子句。 因此，它將不知道count(leads.contact_id)或orders是count(leads.contact_id) 。 HAVING上除后評估GROUP BY 。 它用於過濾聚合。

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

我應該使用HAVING而不是WHERE，因為WHERE僅可用於過濾原始數據表，而不能用於過濾計算出的數據表。 但是列數（leads.contact_id）或訂單是計算列，而不是表的原始列，因此我不得不像這樣使用HAVING使其起作用：

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

另請參閱此詳細說明