Grouping and Aggregating When Querying LINQ to SQL - Aggregations in LINQ (like GROUP BY..HAVING of SQL in LINQ)
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Now, let us consider the following SQL SELECT query:
SELECT CustomerID, SUM(Freight)
FROM Orders
GROUP BY CustomerID
HAVING SUM(Freight) > 200
The above does the aggregation first and then filters the output, applying the HAVING condition. The same can be achieved in VB.NET LINQ as follows:
Dim q = From p In db.Orders _
Group p By p.CustomerID _
Into FreightSum = Sum(p.Freight) _
Where FreightSum > 200 _
Select _
CustomerID, _
FreightSum
And in C# LINQ as follows:
var q = from p in db.Orders
group p.Freight by p.CustomerID
into g
where g.Sum() > 200
select new { CustomerID = g.Key, FreightSum = g.Sum() };
Further flavors for the same in VB.NET LINQ are as follows:
Dim q = From p In db.Orders _
Group p By p.CustomerID _
Into Group _
Where Group.Sum(Function(p) p.Freight) > 200 _
Select _
CustomerID, _
FreightSum = Group.Sum(Function(p) p.Freight)
Dim q = From p In db.Orders _
Group By p.CustomerID _
Into FreightSum = Sum(p.Freight) _
Where FreightSum > 200
Dim q = From p In db.Orders _
Group FreightValue = p.Freight By p.CustomerID _
Into FreightSum = Sum(FreightValue) _
Where FreightSum > 200
In this article, I gave many examples in VB.NET than on C#. Several of them can be written in C# syntax also. If you have any doubts, please post in the discussion area.
We will go further in-depth in my upcoming articles. I hope you enjoyed the article and any suggestions, bugs, errors, enhancements etc. are highly appreciated at http://jagchat.spaces.live.com
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