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Schema Restrictions

The second optional parameter of the GetSchema method is the restrictions that are used to limit the amount of schema information returned, and it is passed to the GetSchema method as an array of strings. The position in the array determines the values that you can pass, and this is equivalent to the restriction number.

For example, the following table describes the restrictions supported by the "Tables" schema collection using the .NET Framework Data Provider for SQL Server. Additional restrictions for SQL Server schema collections are listed at the end of this topic.

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

TABLE_CATALOG

1

Owner

@Owner

TABLE_SCHEMA

2

Table

@Name

TABLE_NAME

3

TableType

@TableType

TABLE_TYPE

4

To use one of the restrictions of the "Tables" schema collection, simply create an array of strings with four elements, then place a value in the element that matches the restriction number. For example, to restrict the tables returned by the GetSchema method to only those tables in the "Sales" schema, set the second element of the array to "Sales" before passing it to the GetSchema method.

Note Note

The restrictions collections for SqlClient and OracleClient have an additional ParameterName column. The restriction default column is still there for backwards compatibility, but is currently ignored. Parameterized queries rather than string replacement should be used to minimize the risk of an SQL injection attack when specifying restriction values.

Note Note

The number of elements in the array must be less than or equal to the number of restrictions supported for the specified schema collection else an ArgumentException will be thrown. There can be fewer than the maximum number of restrictions. The missing restrictions are assumed to be null (unrestricted).

You can query a .NET Framework managed provider to determine the list of supported restrictions by calling the GetSchema method with the name of the restrictions schema collection, which is "Restrictions". This will return a DataTable with a list of the collection names, the restriction names, the default restriction values, and the restriction numbers.

The following examples demonstrate how to use the GetSchema method of the .NET Framework Data Provider for the SQL Server SqlConnection class to retrieve schema information about all of the tables contained in the AdventureWorks sample database, and to restrict the information returned to only those tables in the "Sales" schema:

[Visual Basic]

Imports System.Data.SqlClient

Module Module1
Sub Main()
  Dim connectionString As String = _
    "Data Source=(local);Database=AdventureWorks;" & _
       "Integrated Security=true;";

  Dim restrictions(3) As String
  Using connection As New SqlConnection(connectionString)
    connection.Open()

    'Specify the restrictions.
    restrictions(1) = "Sales"
    Dim table As DataTable = connection.GetSchema("Tables", _
       restrictions)

    ' Display the contents of the table.
      For Each row As DataRow In table.Rows
         For Each col As DataColumn In table.Columns
            Console.WriteLine("{0} = {1}", col.ColumnName, row(col))
         Next
         Console.WriteLine("============================")
      Next
    Console.WriteLine("Press any key to continue.")
    Console.ReadKey()
  End Using
End Sub
End Module

[C#]

using System;
using System.Data;
using System.Data.SqlClient;

class Program
{
  static void Main()
  {
    string connectionString = 
       "Data Source=(local);Database=AdventureWorks;" +
       "Integrated Security=true;";
    using (SqlConnection connection =
       new SqlConnection(connectionString))
    {
        connection.Open();

        // Specify the restrictions.
        string[] restrictions = new string[4];
        restrictions[1] = "Sales";
        System.Data.DataTable table = connection.GetSchema(
          "Tables", restrictions);

        // Display the contents of the table.
        foreach (System.Data.DataRow row in table.Rows)
        {
            foreach (System.Data.DataColumn col in table.Columns)
            {
                Console.WriteLine("{0} = {1}", 
                  col.ColumnName, row[col]);
            }
            Console.WriteLine("============================");
        }
        Console.WriteLine("Press any key to continue.");
        Console.ReadKey();
    }
  }

  private static string GetConnectionString()
  {
     // To avoid storing the connection string in your code,
     // you can retrieve it from a configuration file.
     return "Data Source=(local);Database=AdventureWorks;" +
        "Integrated Security=true;";
  }

  private static void DisplayData(System.Data.DataTable table)
  {
     foreach (System.Data.DataRow row in table.Rows)
     {
        foreach (System.Data.DataColumn col in table.Columns)
        {
           Console.WriteLine("{0} = {1}", col.ColumnName, row[col]);
        }
     Console.WriteLine("============================");
     }
  }
}

The following tables list the restrictions for SQL Server schema collections.

Restriction Name

Parameter Name

Restriction Default

Restriction Number

User_Name

@Name

name

1

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Name

@Name

Name

1

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

TABLE_CATALOG

1

Owner

@Owner

TABLE_SCHEMA

2

Table

@Name

TABLE_NAME

3

TableType

@TableType

TABLE_TYPE

4

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

TABLE_CATALOG

1

Owner

@Owner

TABLE_SCHEMA

2

Table

@Table

TABLE_NAME

3

Column

@Column

COLUMN_NAME

4

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

TABLE_CATALOG

1

Owner

@Owner

TABLE_SCHEMA

2

Table

@Table

TABLE_NAME

3

Column

@Column

COLUMN_NAME

4

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

TABLE_CATALOG

1

Owner

@Owner

TABLE_SCHEMA

2

Table

@Table

TABLE_NAME

3

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

VIEW_CATALOG

1

Owner

@Owner

VIEW_SCHEMA

2

Table

@Table

VIEW_NAME

3

Column

@Column

COLUMN_NAME

4

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

SPECIFIC_CATALOG

1

Owner

@Owner

SPECIFIC_SCHEMA

2

Name

@Name

SPECIFIC_NAME

3

Parameter

@Parameter

PARAMETER_NAME

4

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

SPECIFIC_CATALOG

1

Owner

@Owner

SPECIFIC_SCHEMA

2

Name

@Name

SPECIFIC_NAME

3

Type

@Type

ROUTINE_TYPE

4

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

db_name()

1

Owner

@Owner

user_name()

2

Table

@Table

o.name

3

ConstraintName

@ConstraintName

x.name

4

Column

@Column

c.name

5

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

db_name()

1

Owner

@Owner

user_name()

2

Table

@Table

o.name

3

Restriction Name

Parameter Name

Restriction Default

Restriction Number

assembly_name

@AssemblyName

assemblies.name

1

udt_name

@UDTName

types.assembly_class

2

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

CONSTRAINT_CATALOG

1

Owner

@Owner

CONSTRAINT_SCHEMA

2

Table

@Table

TABLE_NAME

3

Name

@Name

CONSTRAINT_NAME

4

The following tables list the restrictions for SQL Server 2008 schema collections. These restrictions are valid beginning with version 3.5 SP1 of the .NET Framework and SQL Server 2008. They are not supported in earlier versions of the .NET Framework and SQL Server.

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

TABLE_CATALOG

1

Owner

@Owner

TABLE_SCHEMA

2

Table

@Table

TABLE_NAME

3

Restriction Name

Parameter Name

Restriction Default

Restriction Number

Catalog

@Catalog

TABLE_CATALOG

1

Owner

@Owner

TABLE_SCHEMA

2

Table

@Table

TABLE_NAME

3

Column

@Column

COLUMN_NAME

4

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