sql - How to find gaps in sequential numbering in mysql? -

we have database table values imported system. there auto-increment column, , there no duplicate values, there missing values. example, running query:

select count(id) arrc_vouchers id between 1 , 100 

should return 100, returns 87 instead. there query can run return values of missing numbers? example, records may exist id 1-70 , 83-100, there no records id's of 71-82. want return 71, 72, 73, etc.

is possible?

here's version works on table of size (not on 100 rows):

select (t1.id + 1) gap_starts_at,         (select min(t3.id) -1 arrc_vouchers t3 t3.id > t1.id) gap_ends_at arrc_vouchers t1 not exists (select t2.id arrc_vouchers t2 t2.id = t1.id + 1) having gap_ends_at not null 

• gap_starts_at - first id in current gap
• gap_ends_at - last id in current gap