2 Select 个语句，1 个查询 -- Return 2 列

Question

我有 2 个 select 语句，我想在 1 个查询中 return。我目前正在使用 union，它在 1 个查询中 returning 两个结果，但它 returning 2 行...

我想尝试 return 2 列，而不是 2 行。

下面是我的查询：

SELECT distinct count([number]) AS 'Total' from [myTbl] WHERE [type] = 'online' union
SELECT distinct count([number]) AS 'Success' from [myTbl] WHERE [type] = 'online' and [MyValue] = 'true'

我想要 2 列.. Total 和 Success。这可能吗？也许不是通过 union，而是通过其他方法？

Answer 1

这个怎么样？它为每一行求和一个值，设置为 1 表示成功，否则设置为 0，因此计算成功。

SELECT  COUNT([number]) AS 'Total',
        SUM(CASE WHEN [MyValue] = 'true' THEN 1 ELSE 0 END) AS 'Success'
FROM    [myTbl]
WHERE   [type] = 'online'

Answer 2

您可以将其包装在两个子查询中，这样您将获得包含两个结果列的一行。

SELECT
  (SELECT distinct count([number]) FROM [myTbl] WHERE [type]='online') AS Total,
  (SELECT distinct count([number]) FROM [myTbl] WHERE [type]='online' AND [MyValue]='true') AS Success

注意这里DISTINCT的使用存疑

Answer 3

Common Table Expressions 的完美用例。

;WITH CTE_Total AS (
    SELECT DISTINCT COUNT([number]) AS 'Total'
    FROM [myTbl]
    WHERE [type] = 'online'
), CTE_Success AS (
    SELECT DISTINCT COUNT([number]) AS 'Success'
    FROM [myTbl]
    WHERE [type] = 'online' and [MyValue] = 'true'
)
SELECT
    [Total] = CTE_Total.Total,
    [Success] = CTE_Success.Success;

Answer 4

很简单，这样做：

SELECT Total, Success from 
(
    SELECT distinct count([number]) AS 'Total' from [myTbl] WHERE [type] = 'online' union
    SELECT distinct count([number]) AS 'Success' from [myTbl] WHERE [type] = 'online' and [MyValue] = 'true'
)

Answer 5

试试这个

    SELECT 
       (SELECT count([number]) FROM [myTbl] WHERE [type] = 'online') AS 'Total',
       (SELECT count([number]) FROM [myTbl] WHERE [type] = 'online' and [MyValue] = 'true') AS 'Success'

或者更易于维护

    ;WITH tbl as (
        SELECT [number], [MyValue] FROM [myTbl] WHERE [type] = 'online'
    )
    SELECT 
       (SELECT count([number]) FROM tbl) AS 'Total',
       (SELECT count([number]) FROM tbl WHERE [MyValue] = 'true') AS 'Success'

2 Select 个语句，1 个查询 -- Return 2 列

2 Select Statements, 1 Query -- Return 2 Columns

sql-server

union

select