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尋找數值序列中的最大值

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使用 Max 運算子可尋找數值序列中的最高值。

範例 1

下列範例可尋找任何員工的最近雇用日期。

如果您對 Northwind 範例資料庫執行這個查詢，則輸出為：11/15/1994 12:00:00 AM。

System.Nullable<DateTime> latestHireDate =
    (from emp in db.Employees
    select emp.HireDate)
    .Max();

Console.WriteLine(latestHireDate);

Dim latestHireDate = Aggregate emp In db.Employees _
                     Into Max(emp.HireDate)

Console.WriteLine(latestHireDate)

範例 2

下列範例可尋找任何產品的最多庫存單位。

如果您對 Northwind 範例資料庫執行這個範例，則輸出為：125。

System.Nullable<Int16> maxUnitsInStock =
    (from prod in db.Products
    select prod.UnitsInStock)
    .Max();

Console.WriteLine(maxUnitsInStock);

Dim maxUnitsInStock = Aggregate prod In db.Products _
                      Into Max(prod.UnitsInStock)

Console.WriteLine(maxUnitsInStock)

範例 3

下列範例會使用 Max 來尋找各分類中具有最高單價的 Products。 接著，輸出會依照分類列出結果。

var maxQuery =
    from prod in db.Products
    group prod by prod.CategoryID into grouping
    select new
    {
        grouping.Key,
        MostExpensiveProducts =
            from prod2 in grouping
            where prod2.UnitPrice == grouping.Max(prod3 =>
                prod3.UnitPrice)
            select prod2
    };

foreach (var grp in maxQuery)
{
    Console.WriteLine(grp.Key);
    foreach (var listing in grp.MostExpensiveProducts)
    {
        Console.WriteLine(listing.ProductName);
    }
}

Dim maxQuery = From prod In db.Products() _
               Group prod By prod.CategoryID Into grouping = Group _
               Select CategoryID, _
               MostExpensiveProducts = _
                   (From prod2 In grouping _
                    Where prod2.UnitPrice = _
                   grouping.Max(Function(prod3) prod3.UnitPrice))

For Each grp In maxQuery
    Console.WriteLine(grp.CategoryID)
    For Each listing In grp.MostExpensiveProducts
        Console.WriteLine(listing.ProductName)
    Next
Next

如果您對 Northwind 範例資料庫執行前一個查詢，則結果會類似下列：

1

Côte de Blaye

2

Vegie-spread

3

Sir Rodney's Marmalade

4

Raclette Courdavault

5

Gnocchi di nonna Alice

6

Thüringer Rostbratwurst

7

Manjimup Dried Apples

8

Carnarvon Tigers

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