$LISTDATA (SQL)

A list function that indicates whether the specified element exists and has a data value.

Synopsis

$LISTDATA(list[,position])

Description

$LISTDATA checks for data in the requested element in a list. $LISTDATA returns a value of 1 if the element indicated by the position argument is in the list and has a data value. $LISTDATA returns a value of a 0 if the element is not in the list or does not have a data value.

This function returns data of type SMALLINT.

Arguments

list

An encoded character string containing one or more elements. You can create a list using the SQL $LISTBUILD function or the ObjectScript $LISTBUILD function. You can convert a delimited string into a list using the SQL $LISTFROMSTRING function or the ObjectScript $LISTFROMSTRING function. You can extract a list from an existing list using the SQL $LIST function or the ObjectScript $LIST function.

position

If you omit the position argument, $LISTDATA evaluates the first element. If the value of the position argument is -1, it is equivalent to specifying the final element of the list. If the value of the position argument refers to a nonexistent list member, $LISTDATA returns 0.

Examples

The following Embedded SQL examples show the results of the various values of the position argument.

All of the following $LISTDATA statements return a value of 1:

  KILL Y
  SET a=$LISTBUILD("Red",,Y,"","Green")
  &sql(SELECT $LISTDATA(:a), $LISTDATA(:a,1), 
       $LISTDATA(:a,4), $LISTDATA(:a,5), $LISTDATA(:a,-1)
       INTO :b,:c, :d, :e, :f)
  IF SQLCODE'=0 {
    WRITE !,"Error code ",SQLCODE }
  ELSE {
    WRITE !,"1st element status  ",b  ; 1st element default
    WRITE !,"1st element status  ",c  ; 1st element specified
    WRITE !,"4th element status  ",d  ; 4th element null string
    WRITE !,"5th element status  ",e  ; 5th element in 5-element list
    WRITE !,"last element status ",f  ; last element in 5-element list
  }

The following $LISTDATA statements return a value of 0 for the same five-element list:

  KILL Y
  SET a=$LISTBUILD("Red",,Y,"","Green")
  &sql(SELECT $LISTDATA(:a,2), $LISTDATA(:a,3), 
       $LISTDATA(:a,0), $LISTDATA(:a,6)
       INTO :b,:c, :d, :e)
  IF SQLCODE'=0 {
    WRITE !,"Error code ",SQLCODE }
  ELSE {
    WRITE !,"2nd element status ",b  ; 2nd element is undefined
    WRITE !,"3rd element status ",c  ; 3rd element is killed variable
    WRITE !,"0th element status ",d  ; zero position nonexistent
    WRITE !,"6th element status ",e  ; 6th element in 5-element list
  }

Notes

Invalid Argument Values

If the expression in the list argument does not evaluate to a valid list, an SQLCODE -400 fatal error occurs:

   &sql(SELECT $LISTDATA('fred') INTO :b)
   IF SQLCODE'=0 {
     WRITE !,"Error code ",SQLCODE }
   ELSE {
   WRITE !,"The the element is ",b }

If the value of the position argument is less than -1, an SQLCODE -400 fatal error occurs:

   SET a=$LISTBUILD("Red","Blue","Green")
   &sql(SELECT $LISTDATA(:a,-3) INTO :c)
   IF SQLCODE'=0 {
     WRITE !,"Error code ",SQLCODE }
   ELSE {
   WRITE !,"A neg-num position status ",c }

This does not occur when position is a nonnumeric value:

   SET a=$LISTBUILD("Red","Blue","Green")
   &sql(SELECT $LISTDATA(:a,'g') INTO :c)
   IF SQLCODE'=0 {
     WRITE !,"Error code ",SQLCODE }
   ELSE {
     WRITE !,"Error code ",SQLCODE
     WRITE !,"A nonnumeric position status ",c }