Checking Indicator Variables to Test for Returned Null Values

Indicator variables can also be used to test whether a returned value is a null value. This is done by using the indicator variables along with host variables used for output.

The following example shows how to use indicator variables in the INTO clause of a SELECT statement to check for null values.

Example Using Indicator Variables to Check for Returned Null Values

EXEC SQL BEGIN DECLARE SECTION ;

     long    cust_no ;

     char    phone [13] ;

     short   i_phone ;

EXEC SQL END DECLARE SECTION ;

cust_no = 1001 ;

EXEC SQL

     SELECT c_phone

     INTO  :phone:i_phone

     FROM  customer

     WHERE  cust_no = :cust_no ;

if (i_phone == -1)

     printf ("No Phone Number\\n") ;

else

     printf ("Phone Number is %s\\n", phone) ;

For more information on indicator variables, see "NULL Value Handling in ESQL" and "Error Handling in ESQL".