将两个单独查询的结果合并为两列

Question

我正在处理两个我想要组合成一个的SQL查询,因此第一个查询的结果将在第一列中,第二个结果将在第二列中.我该如何实现这一目标？

我试过联盟,但它会把结果分成两行......那不是我想要的......

select count(*) as ColumnA from Inventory i, Sale s where i.vin=s.vin and i.condition='new' 

select count(*) as ColumnB from Inventory i, Sale s where i.vin=s.vin and i.condition='used' order by 1 desc;

Answer 1

您可以使用稍微不同的查询同时获取两个计数,这将比组合两个查询稍微更有效:

SELECT
    SUM(CASE WHEN i.condition = 'new' THEN 1 ELSE 0 END),
    SUM(CASE WHEN i.condition = 'used' THEN 1 ELSE 0 END)
FROM
    Inventory i
JOIN
    Sale s ON i.vin = s.vin

Answer 2

您可以在一个查询中使用组合两个子查询,如下所示:

select
(select count(*) from Inventory i, Sale s where i.vin=s.vin and i.condition='new') as New,
(select count(*) from Inventory i, Sale s where i.vin=s.vin and i.condition='used') as Used

你想通过声明来实现什么目标？