是否可以在同一查询中计算两列 [英] Is it possible to count two columns in the same query

问题描述

假设我具有以下表结构:

Let's say I have the following table structure:

t1
-------------
id // row id
userID_follower // this user is a follows another member
userID_following  // other member that this user 

是否可以运行单个查询来组合以下两个内容:

Is it possible to run a single query to combine both of the following:

1. 此人正在关注多少用户

1. how many users this person is following

从t1中选择COUNT(id)，其中userID_follower =.$ myID". ."

select COUNT(id) from t1 WHERE userID_follower = ".$myID." ."

有多少用户关注此人

how many users follow this person

从t1 WHERE userID_following =.$ myID."中选择COUNT(id).

select COUNT(id) from t1 WHERE userID_following = ".$myID."

谢谢.

推荐答案

在MySql中，可以在条件上使用SUM()函数，因为错误条件将等于0，而真实条件将等于0. 1:

In MySql, You can use the SUM() function over a condition, since a false condition will equal to 0, and a true one will equal to 1:

SELECT SUM(userID_follower = $myID) AS followerCount,
   SUM(userID_following = $myID) AS followingCount
FROM t1
WHERE userID_follower = $myID
   OR userID_following = $myID

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