Example: custdata.4gl (Function cust_name_exists)

The cust_name_exists function verifies that the name passed as parameter is no already used by a customer table row, with a number different from the second parameter.

The cust_name_exists function in custdata.4gl:

  1 PRIVATE FUNCTION cust_name_exists(
  2   curr_name LIKE customer.cust_name,
  3   curr_cust t_cust_num)
  4  RETURNS BOOLEAN
  5   DEFINE name LIKE customer.cust_name
  6   SELECT cust_name INTO name FROM customer
  7    WHERE cust_name = curr_name AND cust_num != curr_cust
  8   RETURN ( SQLCA.SQLCODE == 0 )
  9 END FUNCTION

Note:

Line 1 thru 4 declares the function, with two parameters and a boolean return value.
Line 2 defines the first parameter cust_name with the same data type than the customer.cust_name SQL column.
Line 5 defines a local function variable that will be used in the INTO clause of the SELECT.
Line 6 and 7 executes the SELECT statement checking for an existing customer name that matches the name passed as parameter.
Line 8 performs a boolean expression by comparing SQLCA.SQLCODE to zero, and returns the result of this boolean expression. We expect SQLCA.SQLCODE to equal NOTFOUND (100), so that the function returns FALSE.