我什至不知道我是否以正确的方式进行此查询。
有一个Sandwiches
表,其中包含大约7个字段,其中两个是组合框(Type
和Bread
)。
因此,我进行了一个查询,将所有组合框值组合到一个查询中,如下所示:
SELECT TypesAndBreads.TBName, TypesAndBreads.Type
FROM (SELECT [Sandwiches Types].[Sandwich Type] As TBName, "Sandwich Type" As Type
FROM [Sandwiches Types]
UNION ALL
SELECT Breads.Bread As TBName, "Bread" As Type
FROM Breads) AS TypesAndBreads;
我现在得到表的固定值,我想计算每个
TypesAndBreads.TBName
下的所有三明治。我有这个,只是为了确保它适用于所有三明治:SELECT TypesAndBread.Type, TypesAndBread.TBName,
(SELECT Count(Sandwiches.[SandwichID]) As SandwichCount
FROM Sandwiches) As SandwichCount
FROM TypesAndBread;
但是我想在子查询中引用当前的Type和TBName。像这样:
SELECT TypesAndBread.Type, TypesAndBread.TBName,
(SELECT Count(Sandwiches.[SandwichID]) As SandwichCount
FROM Sandwiches
WHERE Sandwiches.[TypesAndBread.Type] = Sandwiches.[TypesAndBread.TBName]) As SandwichCount
FROM TypesAndBread;
但是,当然这是行不通的。我没想到会,只是想尝试一下。当他们打开此查询将基于的报表时,我正在考虑使用VBA构造查询。
所以我想我的问题是:有没有办法在子查询中引用当前选定的字段?还是有其他方法可以解决此问题?
谢谢您的帮助
编辑:
我的表结构是这样的:
Sandwiches
的字段| SandwichID | Name | Date Added | Chef | Sandwich Type | Bread | Reviewed By |
其中
Sandwich Type
和Bread
是这些表的查找字段:Sandwiches Types
的字段| Sandwich Type |
Breads
的字段| Bread |
TypesAndBreads查询结合了Sandwiches Types和Breads表,但是这样做的原因是,我可以获得具有该Type或面包的所有三明治的计数。结果如下:
+=============================================+
| Type | TBName | SandwichCount |
+=============================================+
| Sandwich Type | Turkey Club | 10 |
| Bread | Italian | 5 |
| Bread | Garlic | 8 |
+---------------------------------------------+
示例结果的第一行基本上说,记录中有10个三明治,“三明治类型”字段等于“土耳其俱乐部”。
我希望可以更好地解释它。
最佳答案
不确定Access是否支持它,但是在大多数引擎(包括SQL Server
)中,这被称为相关子查询,并且运行良好:
SELECT TypesAndBread.Type, TypesAndBread.TBName,
(
SELECT Count(Sandwiches.[SandwichID]) As SandwichCount
FROM Sandwiches
WHERE (Type = 'Sandwich Type' AND Sandwiches.Type = TypesAndBread.TBName)
OR (Type = 'Bread' AND Sandwiches.Bread = TypesAndBread.TBName)
) As SandwichCount
FROM TypesAndBread
通过索引
Type
和Bread
并将子查询分布在UNION
上,可以提高效率:SELECT [Sandwiches Types].[Sandwich Type] As TBName, "Sandwich Type" As Type,
(
SELECT COUNT(*) As SandwichCount
FROM Sandwiches
WHERE Sandwiches.Type = [Sandwiches Types].[Sandwich Type]
)
FROM [Sandwiches Types]
UNION ALL
SELECT [Breads].[Bread] As TBName, "Bread" As Type,
(
SELECT COUNT(*) As SandwichCount
FROM Sandwiches
WHERE Sandwiches.Bread = [Breads].[Bread]
)
FROM [Breads]
关于sql - 选择查询,选择一条选择语句,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/2043845/