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Call SQLColumns on a Table with Sparse Columns

This sample shows how to call SQLColumns on a table with sparse columns that were defined by using ODBC in SQL Server Native Client.

This sample will not work with any version of SQL Server earlier than SQL Server 2008.

For more information about the sparse columns feature, see Sparse Columns Support in SQL Server Native Client.

The first listing is the C++ source code. Change "MyServer" to a valid server name. Make sure your INCLUDE environment variable includes the directory that contains sqlncli.h. If you will build and run this sample as a 32-bit application on a 64-bit operating system, you must create the ODBC data source with the ODBC Administrator in %windir%\SysWOW64\odbcad32.exe.

This sample connects to your computer's default SQL Server instance. To connect to a named instance, change the definition of the ODBC data source to specify the instance using the following format: server\namedinstance. By default, SQL Server Express installs to a named instance.

Compile with /EHsc /D, "UNICODE", and odbc32.lib.

The second (Transact-SQL) code listing deletes the table created by this sample.

// compile with: /EHsc /D "UNICODE" odbc32.lib
#include <windows.h>
#include <stdio.h>
#include <sqlext.h>

#include <sqlncli.h>

#define SUCCESS(x) (!((x) & 0xFFFE))

#define CHKRC(stmt) rc = (stmt); \
   if (!SUCCESS(rc)) \
   throw (RETCODE) rc;

void PrintError(SQLSMALLINT HandleType, SQLHANDLE Handle) {
   RETCODE rc = SQL_SUCCESS;
   SQLTCHAR szSqlState[6], szMessage[1024];
   SQLSMALLINT i = 1, msgLen = 0;
   SQLINTEGER NativeError;

   do {
      i = 1;
      while (SQL_NO_DATA != (rc = SQLGetDiagRec(HandleType, Handle, i, szSqlState, &NativeError, 
         szMessage, sizeof(szMessage)/sizeof(SQLTCHAR), &msgLen)) && SUCCESS(rc)) {
            wprintf(L"SQLState=%s, NativeError=%ld, Message=%s\r\n", szSqlState, NativeError, szMessage);
            i++;
      }
   } 
   while (SQL_NO_DATA != (rc = SQLMoreResults(Handle)) && SUCCESS(rc));
}

#define STR_LEN 128 + 1
#define REM_LEN 254 + 1

void ProcessSQLColumnsResult(SQLHSTMT hstmt) {
   SQLCHAR szSchema[STR_LEN];
   SQLCHAR szCatalog[STR_LEN];
   SQLCHAR szColumnName[STR_LEN];
   SQLCHAR szTableName[STR_LEN];
   SQLCHAR szTypeName[STR_LEN];
   SQLCHAR szRemarks[REM_LEN];
   SQLCHAR szColumnDefault[STR_LEN];
   SQLCHAR szIsNullable[STR_LEN];

   SQLINTEGER ColumnSize;
   SQLINTEGER BufferLength;
   SQLINTEGER CharOctetLength;
   SQLINTEGER OrdinalPosition;

   SQLSMALLINT DataType;
   SQLSMALLINT DecimalDigits;
   SQLSMALLINT NumPrecRadix;
   SQLSMALLINT Nullable;
   SQLSMALLINT SQLDataType;
   SQLSMALLINT DatetimeSubtypeCode;
   SQLLEN cbCatalog;
   SQLLEN cbSchema;
   SQLLEN cbTableName;
   SQLLEN cbColumnName;
   SQLLEN cbDataType;
   SQLLEN cbTypeName;
   SQLLEN cbColumnSize;
   SQLLEN cbBufferLength;
   SQLLEN cbDecimalDigits;
   SQLLEN cbNumPrecRadix;
   SQLLEN cbNullable;
   SQLLEN cbRemarks;
   SQLLEN cbColumnDefault;
   SQLLEN cbSQLDataType;
   SQLLEN cbDatetimeSubtypeCode;
   SQLLEN cbCharOctetLength;
   SQLLEN cbOrdinalPosition;
   SQLLEN cbIsNullable;

   SQLRETURN rc = SQL_SUCCESS;

   CHKRC(SQLColumns(hstmt, L"tempdb", SQL_NTS, L"dbo", SQL_NTS, L"tbl_sparse_test", SQL_NTS, NULL, 0 ));

   // Bind columns in result set to buffers
   SQLBindCol(hstmt, 1,  SQL_C_CHAR,   szCatalog,              STR_LEN,    &cbCatalog);
   SQLBindCol(hstmt, 2,  SQL_C_CHAR,   szSchema,               STR_LEN,    &cbSchema);
   SQLBindCol(hstmt, 3,  SQL_C_CHAR,   szTableName,            STR_LEN,    &cbTableName);
   SQLBindCol(hstmt, 4,  SQL_C_CHAR,   szColumnName,           STR_LEN,    &cbColumnName);
   SQLBindCol(hstmt, 5,  SQL_C_SSHORT, &DataType,              0,          &cbDataType);
   SQLBindCol(hstmt, 6,  SQL_C_CHAR,   szTypeName,             STR_LEN,    &cbTypeName);
   SQLBindCol(hstmt, 7,  SQL_C_SLONG,  &ColumnSize,            0,          &cbColumnSize);
   SQLBindCol(hstmt, 8,  SQL_C_SLONG,  &BufferLength,          0,          &cbBufferLength);
   SQLBindCol(hstmt, 9,  SQL_C_SSHORT, &DecimalDigits,         0,          &cbDecimalDigits);
   SQLBindCol(hstmt, 10, SQL_C_SSHORT, &NumPrecRadix,          0,          &cbNumPrecRadix);
   SQLBindCol(hstmt, 11, SQL_C_SSHORT, &Nullable,              0,          &cbNullable);
   SQLBindCol(hstmt, 12, SQL_C_CHAR,   szRemarks,              REM_LEN,    &cbRemarks);
   SQLBindCol(hstmt, 13, SQL_C_CHAR,   szColumnDefault,        STR_LEN,    &cbColumnDefault);
   SQLBindCol(hstmt, 14, SQL_C_SSHORT, &SQLDataType,           0,          &cbSQLDataType);
   SQLBindCol(hstmt, 15, SQL_C_SSHORT, &DatetimeSubtypeCode,   0,          &cbDatetimeSubtypeCode);
   SQLBindCol(hstmt, 16, SQL_C_SLONG,  &CharOctetLength,       0,          &cbCharOctetLength);
   SQLBindCol(hstmt, 17, SQL_C_SLONG,  &OrdinalPosition,       0,          &cbOrdinalPosition);
   SQLBindCol(hstmt, 18, SQL_C_CHAR,   szIsNullable,           STR_LEN,    &cbIsNullable);

   try {
      while (SQL_SUCCESS == rc) {
         CHKRC(SQLFetch(hstmt));
         wprintf(L"Column name: %hs\tIsNullable: %hs\tType: %hs\n", szColumnName, szIsNullable, szTypeName);
      }
   }
   catch (RETCODE retcode) {
      if (SQL_NO_DATA != retcode)
         throw retcode;
   }
   SQLFreeStmt(hstmt, SQL_CLOSE);
}

int main() {
   RETCODE rc = SQL_SUCCESS;
   HENV henv = SQL_NULL_HENV;
   HDBC hdbc = SQL_NULL_HDBC;
   SQLHSTMT hstmt = SQL_NULL_HSTMT;
   SQLTCHAR * pszConnection = L"DRIVER={SQL Server Native Client 10.0}; Server=MyServer; Trusted_Connection=Yes;";

   try {
      CHKRC(SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HENV, &henv));
      CHKRC(SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0));
      CHKRC(SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc));
      CHKRC(SQLDriverConnect( hdbc, NULL, pszConnection, SQL_NTS, NULL, 0, NULL, SQL_DRIVER_NOPROMPT));
      CHKRC(SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmt));
      CHKRC(SQLExecDirect(hstmt,
         L"if object_id('tempdb.dbo.tbl_sparse_test','U') is not null drop table tempdb.dbo.tbl_sparse_test",
         SQL_NTS));

      // Create a new table
      CHKRC(SQLExecDirect(hstmt,
         L"create table tempdb.dbo.tbl_sparse_test (col1 int SPARSE, col2 int, col3 XML column_set for all_sparse_columns)",
         SQL_NTS));

      // Insert a row into the table
      CHKRC(SQLExecDirect(hstmt,
         L"insert tempdb.dbo.tbl_sparse_test (col1, col2) values (1,2)",
         SQL_NTS));

      wprintf(L"Checking default SQLColumns behavior.\nYou should not see the first sparse column.\n");

      ProcessSQLColumnsResult(hstmt);

      wprintf(L"\nChecking SQLColumns with the statement attribute SQL_SS_NAME_SCOPE_EXTENDED.\nYou should see all the columns\n");
      CHKRC(SQLSetStmtAttr(hstmt, SQL_SOPT_SS_NAME_SCOPE, (SQLPOINTER)SQL_SS_NAME_SCOPE_EXTENDED, SQL_IS_SMALLINT));

      ProcessSQLColumnsResult(hstmt);

      wprintf(L"\nChecking SQLColumns with the statement attribute SQL_SS_NAME_SCOPE_SPARSE_COLUMN_SET.\nYou should see only the sparse columns\n");
      CHKRC(SQLSetStmtAttr(hstmt, SQL_SOPT_SS_NAME_SCOPE, (SQLPOINTER)SQL_SS_NAME_SCOPE_SPARSE_COLUMN_SET, SQL_IS_SMALLINT));

      ProcessSQLColumnsResult(hstmt);

   }
   catch (RETCODE retcode) {
      rc = retcode;
   }

   if (!SUCCESS(rc)) {
      if (hstmt)
         PrintError(SQL_HANDLE_STMT, hstmt);
      else if (hdbc)
         PrintError(SQL_HANDLE_DBC, hdbc);
      else if(henv)
         PrintError(SQL_HANDLE_ENV, henv);
   }

   if (hstmt)
      SQLFreeHandle(SQL_HANDLE_STMT, hstmt);
   if (hdbc) {
      SQLDisconnect(hdbc);
      SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
   }
   if (henv)
      SQLFreeHandle(SQL_HANDLE_ENV, henv);
}
use tempdb
IF EXISTS (SELECT name FROM sysobjects WHERE name = 'tbl_sparse_test')
     DROP TABLE tbl_sparse_test
GO
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