根据聚合函数标准删除记录

Question

我使用的是SQLite3（版本3.8.6），我在数据库中有一个事务列表。我想DELETE有少于10个关联交易的ID的记录。

我可以用它来列出id及其计数值：

SELECT id,count(id) AS cnt FROM purchases GROUP BY id HAVING cnt < 10;

我尝试将此用于DELETE条记录：

DELETE 
    FROM purchases 
WHERE 
    id IN 
    (SELECT id,count(id) AS cnt FROM purchases GROUP BY id HAVING cnt < 10);

然而，这给了我一个错误：

Error: only a single result allowed for a SELECT that is part of an expression

有没有一种优雅的方法来实现这一目标？

Answer 1

试试这个：

DELETE 
    FROM purchases 
WHERE 
    id IN 
    (SELECT id FROM purchases GROUP BY id HAVING count(*) < 10);

Answer 2

SQLite应该怎么做？

id in (select id, count(id) from ...)

IN运算符需要列表，而不是行集。省略指定的count(id)列并直接在count(*)子句中使用having：

id in (select id from purchases group by id having count(*) < 10)

Answer 3

问题出现在id IN (SELECT id,count(id) AS cnt FROM purchases GROUP BY id HAVING cnt < 10);

您使用了SELECT id和count(id)，基本上它会返回2列结果。使用IN关键字时，您需要：id IN '001', '002', '003'...

要解决您的问题，您需要重新排列语法：

DELETE 
FROM purchases 
WHERE 
id IN 
(SELECT id FROM purchases GROUP BY id HAVING count(id) < 10);