table employee id bigint PK not null employee_name varvhar(100) not null employee_number int4 not null id; employee_name; employee_number 1000; Ivanov; 123 WITH ordered AS ( SELECT employee_number, LAG(employee_number) OVER (ORDER BY employee_number) as prev_number FROM employee ) SELECT prev_number + 1 as missing_number FROM ordered WHERE employee_number - prev_number > 1; 1000; name1; 1 1001; name2; 2 1002; name3; 4 1003; name4; 5 with ordered as () select * from ordered