Question

group id   gender   count
-------    ------   -----
01          M       10
01          F       5
02          M       6
03          F       2

选择数据为

groupId   Male Female 
-------   ---- -----  
01         10   5
02          6   0
03          0   2

Answer 1

您必须使用内联视图并加入以执行所需的操作。

您尚未提及表名。我假设为TableName并编写了查询。使用以下内容。

select m.groupId as groupId, m.count as Male,f.count as Female from 
(select groupId, gender, count from tablename where gender = 'M')m join (select groupId, gender, count from tablename where gender = 'F')f on m.groupid = f.groupid

Answer 2

我认为你的表名是test，所以你的查询可能是：

 select tab.groupId, sum(CASE WHEN tab.gender = 'M' THEN tab.count ELSE 0 END) as male, sum(CASE WHEN tab.gender = 'F' THEN tab.count ELSE 0 END) as female from test tab group by tab.groupId order by tab.groupId

Answer 3

一种可能的方式：

with the_table(group_id, gender, count) as(
    select 01,'M',10 union all
    select 01,'F',5 union all
    select 02,'M',6 union all
    select 03,'F',2
)

select coalesce(t1.group_id, t2.group_id) as group_id, coalesce(t1.count, 0) as male, coalesce(t2.count, 0) as female
from 
(select group_id, count from the_table where gender = 'M') t1
full join
(select group_id, count from the_table where gender = 'F') t2
on t1.group_id = t2.group_id

旁注：count是列名的不好选择，它是保留关键字

如何从postgres SQL表中选择数据

3 个答案: