Retrieving Data Type Information

At times, you might need to get information about the data types supported by the data source, for example, precision and scale. You can use the ODBC function SQLGetTypeInfo to do this.

On Windows, you can use ODBC Test to call SQLGetTypeInfo against the ODBC data source to return the data type information. Refer to "Diagnostic Tools" in the DataDirect Connect for ODBC and Connect XE for ODBC Troubleshooting Guide for details about ODBC Test.

On UNIX, Linux, or Windows, an application can call SQLGetTypeInfo. Here is an example of a C function that calls SQLGetTypeInfo and retrieves the information in the form of a SQL result set.

void ODBC_GetTypeInfo(SQLHANDLE hstmt, SQLSMALLINT dataType) 

{ 
    RETCODE rc; 
// There are 19 columns returned by SQLGetTypeInfo.  
// This example displays the first 3. 
// Check the ODBC 3.x specification for more information. 
// Variables to hold the data from each column 
    char             typeName[30]; 
    short            sqlDataType; 
    unsigned long    columnSize; 
    SQLINTEGER       strlenTypeName, 
                     strlenSqlDataType, 
                     strlenColumnSize; 
    rc = SQLGetTypeInfo(hstmt, dataType); 
    if (rc == SQL_SUCCESS) { 
         
// Bind the columns returned by the SQLGetTypeInfo result set. 
        rc = SQLBindCol(hstmt, 1, SQL_C_CHAR, &typeName,
              (SDWORD)sizeof(typeName), &strlenTypeName); 
        rc = SQLBindCol(hstmt, 2, SQL_C_SHORT, &sqlDataType,
              (SDWORD)sizeof(sqlDataType), &strlenSqlDataType); 
        rc = SQLBindCol(hstmt, 3, SQL_C_LONG, &columnSize,
              (SDWORD)sizeof(columnSize), &strlenColumnSize); 
// Print column headings 
         printf ("TypeName      DataType          ColumnSize\n"); 
         printf ("-------------------- ---------- ----------\n"); 
        do { 
// Fetch the results from executing SQLGetTypeInfo 
            rc = SQLFetch(hstmt); 
            if (rc == SQL_ERROR) { 
// Procedure to retrieve errors from the SQLGetTypeInfo function 
                ODBC_GetDiagRec(SQL_HANDLE_STMT, hstmt); 
                break; 
               } 
// Print the results 
         if ((rc == SQL_SUCCESS) || (rc == SQL_SUCCESS_WITH_INFO)) { 
printf ("%-30s %10i %10u\n", typeName, sqlDataType, columnSize); 
             } 
        } while (rc != SQL_NO_DATA); 
    } 
} 

For information about how a database's data types map to the standard ODBC data types, see the appropriate driver chapter in this book.