使用union join postgresql删除列重复项

Question

我想在我的postgresql select语句中隐藏重复的列。 这是sql代码：

SELECT name, amount, cpu, id 
FROM computersystem, stock 
WHERE cpu=id 
UNION 
SELECT name, amount, ram, id 
FROM computersystem, stock 
WHERE ram=id 
ORDER BY name, amount

和当前输出：

Name:AMD Ultimate Overkill amount:2
Name:AMD Ultimate Overkill amount:10
Name:CPU Heavy, Low Graphics amount:2
Name:CPU Heavy, Low Graphics amount:10
Name:Graphics Heavy, Low CPU amount:8
Name:Graphics Heavy, Low CPU amount:10

我需要得到的只是每个名字中的一个

Name:AMD Ultimate Overkill amount:2
Name:CPU Heavy, Low Graphics amount:2
Name:Graphics Heavy, Low CPU amount:8

有快速解决方案吗？

Answer 1

DISTINCT ON可能会解决您的问题。

 SELECT DISTINCT ON (name)
        name,
        amount,
        cpu,
        id
 FROM computersystem, stock 
 WHERE cpu=id 
 UNION SELECT name, amount, ram, id FROM computersystem, stock 
 WHERE ram=id
 GROUP BY name
 ORDER BY name, amount

在此处找到官方文档。