Question

如何将这四个请求合并为一个？

Select COUNT(Table1.statusID) as result1 from Table1 where Table1.emplDesignerID = 1135 and Table1.cancelled = 0
Select COUNT(Table1.statusID) as result2 from Table1 where Table1.emplDesignerID = 26 and Table1.cancelled = 0
Select COUNT(Table1.statusID) as result3 from Table1 where Table1.emplDesignerID = 1086 and Table1.cancelled = 0
Select COUNT(Table1.statusID) as result4 from Table1 where Table1.emplDesignerID = 1089 and Table1.cancelled = 0

我正在使用MS SQL Server。

Answer 1

SUM和CASE可以在这里有用地组合：

Select
    SUM(CASE WHEN Table1.emplDesignerID = 1135 THEN 1 ELSE 0 END) as result1,
    SUM(CASE WHEN Table1.emplDesignerID = 26 THEN 1 ELSE 0 END) as result2,
    SUM(CASE WHEN Table1.emplDesignerID = 1086 THEN 1 ELSE 0 END) as result3,
    SUM(CASE WHEN Table1.emplDesignerID = 1089 THEN 1 ELSE 0 END) as result4
from Table1
where Table1.cancelled = 0
and Table1.emplDesignerID in (1135,26,1086,1089)

根据使用情况，您可能会或可能不会认为IN子句中需要WHERE过滤器。还有其他可能的转换（在emplDesignerID子句中包含SELECT，并在其上加上GROUP），这可能会使它更加灵活。

Answer 2

您可以简单地使用子查询，并将其组合为一个更大的查询。

select
(
Select COUNT(Table1.statusID) as result1 from Table1 where Table1.emplDesignerID = 1135 and Table1.cancelled = 0
) as result1, 
(
Select COUNT(Table1.statusID) as result2 from Costs where Table1.emplDesignerID = 26 and Table1.cancelled = 0
) as result2,
(
Select COUNT(Table1.statusID) as result3 from Costs where Table1.emplDesignerID = 1086 and Table1.cancelled = 0
) as result3,
(
Select COUNT(Table1.statusID) as result4 from Costs where Table1.emplDesignerID = 1089 and Table1.cancelled = 0
) as result4;

如果您使用的是Oracle，则必须添加from dual。

某些其他数据库（例如MS SQL）不需要它。

更新-符合SQL-92标准

Oracle提供了双重表，因此可以添加附加的from dual。 MS SQL提供了不使用from语句进行查询的功能。

请参见SELECT from nothing?

或者让我们拥有Values功能：

select ( Select COUNT(Table1.statusID) as result1 from Table1 where Table1.emplDesignerID = 1135 and Table1.cancelled = 0 ) as result1, ( Select COUNT(Table1.statusID) as result2 from Costs where Table1.emplDesignerID = 26 and Table1.cancelled = 0 ) as result2, ( Select COUNT(Table1.statusID) as result3 from Costs where Table1.emplDesignerID = 1086 and Table1.cancelled = 0 ) as result3, ( Select COUNT(Table1.statusID) as result4 from Costs where Table1.emplDesignerID = 1089 and Table1.cancelled = 0 ) as result4 from (VALUES ('dummyValue'));

Answer 3

如果只有count（）是您需要的结果，则可以使用UNION：

Select COUNT(Table1.statusID) as result1 from Table1 where Table1.emplDesignerID = 1135 and Table1.cancelled = 0
UNION 
Select COUNT(Table1.statusID) as result2 from Table1 where Table1.emplDesignerID = 26 and Table1.cancelled = 0
UNION 
Select COUNT(Table1.statusID) as result3 from Table1 where Table1.emplDesignerID = 1086 and Table1.cancelled = 0
UNION 
Select COUNT(Table1.statusID) as result4 from Table1 where Table1.emplDesignerID = 1089 and Table1.cancelled = 0

它很容易阅读，但效率不高

如何将这四个请求合并为一个？

3 个答案:

更新-符合SQL-92标准