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
Specifying Restriction Values
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
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
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.
Example
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:
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
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("============================");
}
}
}
SQL Server Schema Restrictions
The following tables list the restrictions for SQL Server schema collections.
Users
Restriction Name
Parameter Name
Restriction Default
Restriction Number
User_Name
@Name
name
1
Databases
Restriction Name
Parameter Name
Restriction Default
Restriction Number
Name
@Name
Name
1
Tables
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
Columns
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
StructuredTypeMembers
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
Views
Restriction Name
Parameter Name
Restriction Default
Restriction Number
Catalog
@Catalog
TABLE_CATALOG
1
Owner
@Owner
TABLE_SCHEMA
2
Table
@Table
TABLE_NAME
3
ViewColumns
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
ProcedureParameters
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
Procedures
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
IndexColumns
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
Indexes
Restriction Name
Parameter Name
Restriction Default
Restriction Number
Catalog
@Catalog
db_name()
1
Owner
@Owner
user_name()
2
Table
@Table
o.name
3
UserDefinedTypes
Restriction Name
Parameter Name
Restriction Default
Restriction Number
assembly_name
@AssemblyName
assemblies.name
1
udt_name
@UDTName
types.assembly_class
2
ForeignKeys
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
SQL Server 2008 Schema Restrictions
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.