将来自两个单独查询的结果合并到两列中

Question

我正在处理两个SQL查询，我想将它们合并为一个，因此第一个查询的结果将在第一列中，而第二个查询的结果将在第二列中。 我该如何实现？

我尝试了联合，但它将结果分成两行..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

您可以通过稍有不同的查询同时获得两个计数，这将比组合两个查询的效率略高：

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两个子查询合并，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

您试图通过按订单实现什么？

Answer 3

一种简单的方法是：

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

Answer 4

您可以使用另一个SELECT合并结果：

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