Свойство Column.IsPersisted

Статья
04/26/2013

Gets the Boolean property value that specifies whether the computed value of the Column object is saved with the data, thus avoiding a computation each time the column is accessed.

Пространство имен: Microsoft.SqlServer.Management.Smo
Сборка: Microsoft.SqlServer.Smo (в Microsoft.SqlServer.Smo.dll)

Синтаксис

'Декларация
<SfcPropertyAttribute(SfcPropertyFlags.None Or SfcPropertyFlags.Standalone Or SfcPropertyFlags.SqlAzureDatabase Or SfcPropertyFlags.Design)> _
Public Property IsPersisted As Boolean 
    Get 
    Set
'Применение
Dim instance As Column 
Dim value As Boolean 

value = instance.IsPersisted

instance.IsPersisted = value

[SfcPropertyAttribute(SfcPropertyFlags.None|SfcPropertyFlags.Standalone|SfcPropertyFlags.SqlAzureDatabase|SfcPropertyFlags.Design)]
public bool IsPersisted { get; set; }

[SfcPropertyAttribute(SfcPropertyFlags::None|SfcPropertyFlags::Standalone|SfcPropertyFlags::SqlAzureDatabase|SfcPropertyFlags::Design)]
public:
property bool IsPersisted {
    bool get ();
    void set (bool value);
}

[<SfcPropertyAttribute(SfcPropertyFlags.None|SfcPropertyFlags.Standalone|SfcPropertyFlags.SqlAzureDatabase|SfcPropertyFlags.Design)>]
member IsPersisted : bool with get, set

function get IsPersisted () : boolean 
function set IsPersisted (value : boolean)

Значение свойства

Тип: System.Boolean
A Boolean property value that specifies whether the computed value of the Column object is saved with the data.If True, the computed value of the Column object is saved with the data.If False (default), the computed value of the Column object is computed every time the column data is requested. The IsPersisted property can only be set to True for computed columns. Otherwise, it will cause an error.

Замечания

The following example shows how to use feature in C#:

// compile with: /r:Microsoft.SqlServer.Smo.dll /r:Microsoft.SqlServer.ConnectionInfo.dll /r:Microsoft.SqlServer.Management.Sdk.Sfc.dll 
using System;
using Microsoft.SqlServer.Management.Smo;

public class A {
   public static void Main() {
      Server svr = new Server(); 
      Database db = new Database(svr, "TestDB");
      db.Create();

      Table tab1 = new Table(db, "Table1");

      Column col1 = new Column(tab1, "Col1", DataType.Int);

      // Computed column
      Column col2 = new Column(tab1, "Col2", DataType.Int);
      col2.Computed = true;
      col2.ComputedText = "col1 * 2";

      // Persisted Computed Column
      Column col3 = new Column(tab1, "Col3", DataType.Int);
      col3.Computed = true;
      col3.ComputedText = "col1 * 3";

      // allows the computed column to persist with table data
      col3.IsPersisted = true;   

      tab1.Columns.Add(col1);
      tab1.Columns.Add(col2);
      tab1.Columns.Add(col3);

      tab1.Create();

      // default value of IsPersisted for computed column is false
      Console.WriteLine(col2.Name + "  Computed = " + col2.Computed + "  Persisted =  " + col2.IsPersisted);
      Console.WriteLine(col3.Name + "  Computed = " + col3.Computed + "  Persisted =  " + col3.IsPersisted);
   }
}

The following example shows how to use feature in Visual Basic:

' compile with: /r:Microsoft.SqlServer.Smo.dll /r:Microsoft.SqlServer.ConnectionInfo.dll /r:Microsoft.SqlServer.Management.Sdk.Sfc.dll
Imports Microsoft.SqlServer.Management.Smo

Public Class A
   Public Shared Sub Main()
      Dim svr As New Server()
      Dim db As New Database(svr, "TestDB")
      db.Create()

      Dim tab1 As New Table(db, "Table1")

      Dim col1 As New Column(tab1, "Col1", DataType.Int)

      ' Computed column
      Dim col2 As New Column(tab1, "Col2", DataType.Int)
      col2.Computed = True
      col2.ComputedText = "col1 * 2"

      ' Persisted Computed Column
      Dim col3 As New Column(tab1, "Col3", DataType.Int)
      col3.Computed = True
      col3.ComputedText = "col1 * 3"

      ' allows the computed column to persist with table data
      col3.IsPersisted = True

      tab1.Columns.Add(col1)
      tab1.Columns.Add(col2)
      tab1.Columns.Add(col3)

      tab1.Create()

      ' default value of IsPersisted for computed column is false
      Console.WriteLine((col2.Name & "  Computed = " & col2.Computed & "  Persisted =  ") & col2.IsPersisted)
      Console.WriteLine((col3.Name & "  Computed = " & col3.Computed & "  Persisted =  ") & col3.IsPersisted)
   End Sub
End Class

См. также

Справочник

Column Класс

Пространство имен Microsoft.SqlServer.Management.Smo

Другие ресурсы

Работа с объектами базы данных

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