Hi,

Using unique constraint of SQL, you can avoid duplication of record. For example, if you want to restrict the user to create record which has same name, you can apply constraint like below:

_sql_constraints = [
     ('name_uniq', 'unique(name)', 'Name must be unique!'),
 ]

You can also apply more than 1 field in constraint. You can refer constraint of hr.job object from hr.py file of HR module.

Hope this may help you.