Find missing sequence gaps mysql [duplicate]

Answer 1

You can't return the rows that are missing without a list of all possible numerical values to LEFT JOIN against.

This query (which feels like it could be better/stronger/faster, but it works) will find you the gaps:

set @last_prefix = null;
set @last_value = null;
select result from (
    select @last_prefix, @last_value, name,
      @prefix := substring(name,1,3) as prefix,
      @value := substring(name,4) as value,
      case when @prefix = @last_prefix and @value != @last_value +1
        then concat ("gap from ", @prefix, ": ", @last_value+1, " to ", @value-1)
        else "ok" end as result,
      @last_prefix := @prefix, @last_value := @value
      from t20120921
) foo
where result != "ok";