Example: orders.4gl (Function item_update)

This function implements the SQL row modification for an order item row.

Function item_update (orders.4gl):

  1 PRIVATE FUNCTION item_update(x INTEGER) RETURNS BOOLEAN
  2 
  3   TRY
  4      UPDATE items SET
  5               quantity  = orditems[x].quantity
  6         WHERE items.stock_num = orditems[x].stock_num
  7           AND items.order_num = order_rec.order_num
  8   CATCH   
  9      CALL comutils.mbox_ok(title2,SQLERRMESSAGE)
 10      RETURN FALSE
 11   END TRY
 12 
 13   MESSAGE msg09
 14   CALL comp_order_total()
 15   RETURN TRUE
 16 
 17 END FUNCTION

Note:

Line 1 declares the function with the x integer parameter representing the index in the orditems array, and returns a boolean to indicate if the SQL command succeeds.
Lines 4 thru 7 implement the SQL UPDATE command, to modify the row from the items table that has the stock_num equal to the current order item of the list (orditems[x].stock_num), and the order number equal to the current order number (order_rec.order_num)
Lines 9 and 10 are executed when an SQL error occurs, and returns from the function with FALSE.
Line 13 shows a message to the user to indicate that the SQL operation succeeded.
Line 14 re-computes the order total by calling the comp_order_total function.
Line 15 returns TRUE to the caller.