Retrieving Data

Retrieve data from a database using SQL statements.

1. Execute a select statement using SQLExecute or SQLExecDirect to retrieve rows from a database.
   This opens a cursor on the statement.
2. Use SQLFetch or SQLFetchScroll with SQL_FETCH_NEXT option to fetch rows through the cursor.

   When an application frees the statement using SQLFreeStmt with SQL_CLOSE option, it closes the cursor.

3. Fetch values from a cursor using either SQLBindCol or SQLGetData:

   • If you use SQLBindCol, values are automatically retrieved on each fetch.

   • If you use SQLGetData, you must call it for each column after each fetch.

   SQLGetData is used to fetch values in pieces for columns such as LONG VARCHAR or LONG BINARY.

4. Optionally, set the SQL_ATTR_MAX_LENGTH statement attribute to a value large enough to hold the entire value for the column.
   For SQL_ATTR_MAX_LENGTH, the default value is 32KB.

   This code fragment from the simple sample opens a cursor on a query and retrieves data through the cursor. Error checking has been omitted to make the example easier to read.

   SQLExecDirect( stmt, "select au_fname from authors",
      SQL_NTS ) ;
   retcode = SQLBindCol( stmt, 1, SQL_C_CHAR, aufName,
      sizeof(aufName), &aufNameLen);
   while(retcode == SQL_SUCCESS || retcode ==    SQL_SUCCESS_WITH_INFO)
   {
      retcode = SQLFetch( stmt );
   }