Question

我正在处理两个我希望合并为一个的SQL查询，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。我怎么能实现这个目标呢？

我尝试过联盟，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，这比组合两个查询稍微有效：

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？

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

您可以使用其他SELECT来合并结果：

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

将两个单独查询的结果合并为两列

4 个答案: