Field Activations on Entry and Exit
The 4GL statements that accompany a field activation are executed whenever the user enters or leaves the field, as in this example:
field empnum =
begin
if empnum = 0 or empnum is null then
message
"Please enter an employee number";
sleep 3;
else
empform := retrieve (employee.fname,
employee.lname)
where employee.num = empnum;
resume field "lname";
endif;
end
When the user leaves the empnum field, Ingres checks the value in the field.
• If the value in the field is zero, it issues the error message and returns the cursor to the empnum field.
• If the value in the field is not zero, it retrieves the employee's name from the database and positions the cursor at the lname field.