Question

我有桌子：

stations (staion , phone , address)

AND

members (username , password , fullname , station)

我想要站点列表，计算用户名。所以我写了这个查询。

SELECT 
    stations.station as st,
    (
        SELECT COUNT(username) 
        FROM members 
        WHERE members.station = stations.station
    ) as co
FROM stations
GROUP BY stations.station
ORDER BY stations.station

警告（错误）：

'ERROR: subquery uses ungrouped column "stations.station" from outer query'

请帮我用PostgreSQL获取正确的数据。

Answer 1

正确的解决方案是：

SELECT 
stations.station as st,
(
    SELECT COUNT(username) 
    FROM members 
    WHERE members.station = ANY( array_agg( stations.station ) )
) as co
FROM stations
GROUP BY stations.station
ORDER BY stations.station

Answer 2

试试这个

select stations.station as st,count(username) as co 
from member left join stations on member.station=stations.station 
group by stations.station 
order by stations.station;

Answer 3

没有join的简单回答是：

SELECT  stations.station, COUNT(username)
FROM stations, members
WHERE members.station = stations.station
GROUP BY stations.station
ORDER BY stations.station

在postgresql获取列表中选择子查询

3 个答案: