If you want to avoid deleting record on a table that has child record related to other table just follow this instructions.
You must create a relation between Table “Al0VendorActivity” and “Al0VendorSearcCriteria”. We want to avoid delete record from “Al0VendorActivity” if at least one record exists in the table “Al0VendorSearcCriteria”.
Create a relation between the two tables
Set “On Delete” property to “Restricted” and “Related table” property to “Al0VendorSearchCriteria”
Set join links between the 2 tables
If you try to delete a record from Al0VendorActivity this error occurs, because it has at least one relation with Al0VendorSearchCrieria
Similarly if you try to delete a record from Al0VendorSearchCriteria this error appears