Hello everyone,
For my first application on APEX, I created this form and this table.
The columns of my table USER_CREATION, USER_MODIFICATION, DATE_CREATION, DATE_MODIFICATION and EXCEPTION_ACCESS are automatically submit with a trigger. All others fields are submit with the form below.



Here is an exemple of a trigger I use for submit automatically the column USER_CREATION.
All data submited is visible in page with an interactive grid.

The problem is: when I submit the same information as the one already stored in the table by changing only the value of ID_REPORT, I get the following error and the information is submitted anyway.

Moreover, the goal of my form is to have no duplicates on the combination of these 4 fields: EMPLOYEE_GIVE, EMPLOYEE_GET, REPORT_ID and EXCEPTION_TYPE.
Please could you me help, give me a solution for my two problems that I think are linked.
Thanks in adavance