SQL Table Subsets

The mapping between an SQL table and a Zim EntitySet or data relationship need not be complete with respect to the set of columns owned by the table. Zim retrieves only the columns required from an SQL table; it generates the minimal "select-column-list" to satisfy the requirements of the corresponding Zim command. The Zim Definition Interface imports all the columns of an SQL table translated into Zim field definitions, but only those fields relevant to the application being developed need be used. Also, the defined sequence of the fields in a Zim EntitySet or data relationship need not correspond to that of the columns of the SQL table to which it maps.

It is important to note that if Zim "ADD" commands are to be executed against an SQL table whose Zim field list is a subset of the complete table column list, then those table columns which are not included in the Zim definition must enable the value NULL. An "INSERT" statement generated by Zim cannot specify values for columns about which it has no knowledge.