T-SQL从不同的表中选择并计数吗? [英] T-SQL Select and count from different table?

问题描述

我有一个表( Threads )，其中包含一个字段( id ).我想从 Threads 中选择每一行，以及表 Posts 中的行数，其中字段 Posts.thread 是与 Threads.id 相同.

I have a table (Threads) containing a field (id). I would like to select every row from Threads, as well as the number of rows in the table Posts where the field Posts.thread is the same as Threads.id.

如何在SQL中完成此操作?

How can this be done in SQL?

(类似于这种伪SQL: SELECT *，COUNT(* FROM Posts WHERE Posts.id = Threads.id)FROM Threads )

(Something like this pseudo-SQL: SELECT *, COUNT(* FROM Posts WHERE Posts.id=Threads.id) FROM Threads)

推荐答案

SELECT t.id, COUNT(p.thread)
FROM Threads AS t
    LEFT OUTER JOIN Posts AS p
        ON t.id = p.thread
GROUP BY t.id

这篇关于T-SQL从不同的表中选择并计数吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！