This section describes how to access information about foreign keys by retrieving the ForeignKeys schema collection.

Retrieving Foreign Key Information

To retrieve the ForeignKeys schema collection, call the GetSchema method of the ApachePhoenixConnection class. You can restrict foreign key information by the catalog, schema, or table name.

Access the results in the DataTable returned. The following example lists the foreign keys for the [SampleCatalog_1].[SampleSchema_1].SampleTable_1 table.

C#

String connectionString = "URL=http://localhost:8765;";

using (ApachePhoenixConnection conn = new ApachePhoenixConnection(connectionString)) {
  conn.Open();
  DataTable databaseSchema = conn.GetSchema("ForeignKeys", new string[] {"SampleCatalog_1","SampleSchema_1","SampleTable_1"});
  foreach (DataRow row in databaseSchema.Rows) {
    Console.WriteLine(row["CONSTRAINT_NAME"]);
    Console.WriteLine(row["TABLE_NAME"]);
  }
}

VB.NET

Dim connectionString As String = "URL=http://localhost:8765;"

Using conn As New ApachePhoenixConnection(connectionString)
  conn.Open()
  Dim databaseSchema As DataTable = conn.GetSchema("ForeignKeys",  New String() {"SampleCatalog_1","SampleSchema_1","SampleTable_1")
    For Each row As DataRow In databaseSchema.Rows
    Console.WriteLine(row("CONSTRAINT_NAME"))
    Console.WriteLine(row("TABLE_NAME"))
  Next

End Using

Columns Returned

The ForeignKeys schema collection returns the following information about the foreign keys in Apache Phoenix.