我有一个SQL SELECT查询，也使用GROUP BY， 我想统计GROUP BY子句过滤结果集后的所有记录。
有什么方法可以直接用SQL做到这一点吗?例如，如果我有用户表，想要选择不同的城镇和用户总数:
SELECT `town`, COUNT(*)
FROM `user`
GROUP BY `town`;
我想有一个列的所有城镇和另一个与用户的数量在所有行。
一个有3个镇和58个用户的结果的例子是:
| Town | Count |
|---|---|
| Copenhagen | 58 |
| New York | 58 |
| Athens | 58 |
当前回答
另一种方法是:
/* Number of rows in a derived table called d1. */
select count(*) from
(
/* Number of times each town appears in user. */
select town, count(*)
from user
group by town
) d1
其他回答
如果你想使用Select All Query With Count选项，试试这个…
select a.*, (Select count(b.name) from table_name as b where Condition) as totCount from table_name as a where where Condition
这将做你想做的(城镇列表，每个城镇的用户数量):
SELECT `town`, COUNT(`town`)
FROM `user`
GROUP BY `town`;
在使用GROUP BY语句时，可以使用大多数聚合函数 (COUNT, MAX, COUNT DISTINCT等)
更新: 你可以为用户数量声明一个变量并保存结果，然后选择变量的值:
DECLARE @numOfUsers INT
SET @numOfUsers = SELECT COUNT(*) FROM `user`;
SELECT DISTINCT `town`, @numOfUsers FROM `user`;
你可以使用COUNT(DISTINCT…):
SELECT COUNT(DISTINCT town)
FROM user
如果你想按计数排序(听起来很简单，但我无法在如何做到这一点的堆栈上找到答案)，你可以这样做:
SELECT town, count(town) as total FROM user
GROUP BY town ORDER BY total DESC
如果你想选择城镇和总用户数量，你可以使用下面的查询:
SELECT Town, (SELECT Count(*) FROM User) `Count` FROM user GROUP BY Town;
