INFORMIX-ESQL/C Programmer's Manual ESQL/C Function Library

The risnull() function checks whether a C or an ESQL/C variable contains a null value.

mint risnull(type;  ptrvar)

	mint  type;

	char  *ptrvar;

 



type

is an integer that corresponds to the data type of a C or ESQL/C variable. This type can be any data type except var binary or an lvarchar pointer variable. For more information, see Data Type Constants.


ptrvar  

is a pointer to the C or ESQL/C variable. 

The risnull() function determines whether ESQL/C variables of all data types except var binary and lvarchar pointer variables contain a null value. To determine whether a var binary or lvarchar pointer host variable contains null, use the ifx_var_isnull() macro. For more information, see page B-258.

This sample program is in the risnull.ec file in the demo directory.

/*
* risnull.ec *

This program checks the paid_date column of the orders table for NULL
to determine whether an order has been paid.
*/

#include <stdio.h>

EXEC SQL include sqltypes;

#define WARNNOTIFY 1
#define NOWARNNOTIFY 0

main()
{
char ans;
int4 ret, exp_chk();

EXEC SQL BEGIN DECLARE SECTION;
int4 order_num;

mint order_date, ship_date, paid_date;
EXEC SQL END DECLARE SECTION;

printf("RISNULL Sample ESQL Program running.\n\n");
EXEC SQL connect to 'stores7'; /* open stores7 database*/
exp_chk("CONNECT TO stores7", NOWARNNOTIFY)

EXEC SQL declare c cursor for
select order_num, order_date, ship_date, paid_date from orders;
EXEC SQL open c;
if(exp_chk("OPEN c", WARNNOTIFY) == 1) /* Found warnings */
exit(1);
printf("\n Order#\tPaid?\n"); /* print column hdgs */
while(1)
{
EXEC SQL fetch c into :order_num, :order_date, :ship_date, :paid_date;
if ((ret = exp_chk("FETCH c")) == 100) /* if end of rows */
break; /* terminate loop */
if(ret < 0)
exit(1);
printf("%5d\t", order_num);
if (risnull(CDATETYPE, (char *)&paid_date)) /* is price NULL ? */
printf("NO\n");
else
printf("Yes\n");
}
printf("\nRISNULL Sample Program over.\n\n");
}

/*
* The exp_chk() file contains the exception handling functions to
* check the SQLSTATE status variable to see if an error has occurred
* following an SQL statement. If a warning or an error has
* occurred, exp_chk() executes the GET DIAGNOSTICS statement and
* prints the detail for each exception that is returned.
*/

EXEC SQL include exp_chk.ec

For a complete listing of the exp_chk() function, see Guide to the exp_chk.ec File or refer to the exp_chk.ec file for a listing of this exception-handling function.

RISNULL Sample ESQL Program running.


Order# Paid?
1001 Yes
1002 Yes
1003 Yes
1004 NO
1005 Yes
1006 NO
1007 NO
1008 Yes
1009 Yes
1010 Yes
1011 Yes
1012 NO
1013 Yes
1014 Yes
1015 Yes
1016 NO
1017 NO
1018 Yes
1019 Yes
1020 Yes
1021 Yes
1022 Yes
1023 Yes

RISNULL Sample Program over.