Simplifying data access with queries

Structures of NAV client application language allow accessing only one table at a time, there is no C/AL structure that would enable a table join in one statement. This limitation often affects the performance of C/AL code, forcing the developer to use loops on table records where a single query would be sufficient. With a Query object, developers can overcome this limitation and create queries joining several tables.

How to do it...

In this recipe, we will create a query object calculating profit per item, and use the query as a data source for a page.

1. In the first step, we will add a field to the Item table that will specify if an item certificate is required to post an item entry. Open the table 27 Item in table designer and insert the field:

   Field No.	Field Name	Data Type
   50100	Certificate Required	Boolean

2. Save the modification in the table. Switch to the page designer and open the page 30 Item Card. Insert the field Certificate Required in...