create table tbl (id int);
insert into tbl values (3),(4),(5);
select count(*) anomaly from (
select id - (lag(id) over (order by id)) diff from tbl
) t where diff is not null and diff <> 1;
insert into tbl values (5),(7),(8);
select count(*) anomaly from (
select id - (lag(id) over (order by id)) diff from tbl
) t where diff is not null and diff <> 1;