public override DataTable GetColumns(string[] restrictions)
{
string[] keys = new string[4];
keys[0] = "TABLE_CATALOG";
keys[1] = "TABLE_SCHEMA";
keys[2] = "TABLE_NAME";
keys[3] = "COLUMN_NAME";
DataTable dt = Query("COLUMNS", null, keys, restrictions);
dt.Columns.Remove("CHARACTER_OCTET_LENGTH");
dt.TableName = "Columns";
return dt;
}