vb.net 使用 GROUP BY 对多个字段、SUM 和 COUNT 进行 Linq 查询
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Linq query with GROUP BY on multiple fields, SUM and COUNT
提问by Bastien Vandamme
I'm trying to use a LINQ SQL to query my database.
我正在尝试使用 LINQ SQL 来查询我的数据库。
Let's say I have some data that looks like this:
假设我有一些看起来像这样的数据：
var1 var2 var3 qty
1 a 1a 50
1 a 1a 25
2 b 2b 10
2 b 2b 15
2 b 2b 10
3 a 3a 25
I know how to format my query in SQL. It would be something like this:
我知道如何在 SQL 中格式化我的查询。它会是这样的：
SELECT var1, var2, var3, count(*) AS count, sum(qty) As quantity
FROM MyTable
GROUP BY var1, var2, var3
In this case the output would be something like this:
在这种情况下，输出将是这样的：
var1 var2 var3 Count Qty
1 a 1a 2 75
2 b 2b 3 35
3 a 3a 1 25
How can I do the same thing with LINQ in vb.net
如何在 vb.net 中用 LINQ 做同样的事情
Dim groups = From j In MyTable
Group By j.var1, j.var2, j.var3 Into g
Select new {var1 = g.var1,
var2 = g.var2,
var3 = g.var3,
quantity = sum(g.qty),
count = count(*)}
That's not quite right, but I think it's close. I don't understand the syntax of the group by in VB.NET.
这不太正确，但我认为它很接近。我不明白 VB.NET 中 group by 的语法。
采纳答案by Tim Schmelter
You want to group by an anonymous type, this is the syntax in VB.NET (note the Key):
您想按匿名类型分组，这是 VB.NET 中的语法（注意Key）：
Dim groups =
From j In MyTable
Group By x = New With {Key .var1 = j.var1, Key .var2 = j.var2, Key .var3 = j.var3} Into g = Group
Select New With {
.var1 = x.var1,
.var2 = x.var2,
.var3 = x.var3,
.quantity = g.Sum(Function(r) r.qty),
.count = g.Count()
}
回答by Rahul Singh
You will have to use anonymous typelike this:-
您将不得不使用这样的匿名类型：-
Group j By Key = New With { Key .Var1 = j.var1,
Key .Var2 = j.var2,
Key .Var3 = j.var3 } Into Group
Select New With { .var1 = Key.Var1,
.var2 = Key.Var2,
.var3 = Key.Var3,
.quantity = Group.Sum(Function(x) x.qty),
.count = Group.Count()
}
