mariadb 计算由带有JOIN的嵌套SQL select语句生成的行数

2w3kk1z5 于 2022-11-08 发布在其他

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我有以下SQL语句。

SELECT COUNT(a.id), a.project_id, p.is_recommended 
FROM assessments a 
INNER JOIN projects p ON p.id=a.project_id 
WHERE p.is_recommended = 1 
GROUP BY project_id 
HAVING COUNT(a.id) >= 3

我想计算一下结果的行数。
如果没有INNER JOIN，我所要做的就是这样的事情...

SELECT * FROM
   (SELECT COUNT(id), project_id
    FROM assessments 
    GROUP BY project_id 
    HAVING COUNT(id) >= 3) assessments

但是，如果我的语句包含JOIN，我该如何计算结果行数？我应该使用什么语法？

mariadb

来源：https://stackoverflow.com/questions/73312617/counting-number-of-rows-resulting-from-a-nested-sql-select-statement-with-a-join

1条答案

按热度按时间

8e2ybdfx1#

SELECT COUNT(*)
FROM (SELECT COUNT(a.id), a.project_id, p.is_recommended
    FROM assessments a
    INNER JOIN projects p ON p.id=a.project_id
    WHERE p.is_recommended = 1
    GROUP BY project_id
    HAVING COUNT(a.id) >= 3
    ) AS counts

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mariadb 计算由带有JOIN的嵌套SQL select语句生成的行数

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