MySQL-检查VARCHAR列的增量是否缺少值

Question

I'm trying to find out if my values inserted are auto-incrementing correctly or if for any reason one has failed to be inserted, deleted or gone "missing". I've tried several answers from Stackoverflow but they were mainly pointing out autoincrementable int values so they did not help since mine is a VARCHAR value that follows the following sequence:

AA000001
AA000002
...
AA000100
...
AA213978

and so on...

Thanks for your time.

Answer 1

You can declare SQL Vars in Query and calculate the difference in each iteration, as shown in the example below:

Schema

create table MyTable
(   ai int auto_increment primary key,
    id varchar(100) not null
);
insert MyTable (id) values
('AA000001'),
('AA000002'),
('AA000005'),
('AA000008'),
('AA000009'),
('AA000010');

Query

select id 
FROM 
( 
    select 
      t.id, 
      SUBSTRING(t.id,3) as s, 
      CAST(SUBSTRING(t.id,3) AS UNSIGNED) - @lastId as diff, 
      if( @lastId = 0, 0, CAST(SUBSTRING(t.id,3) AS UNSIGNED) - @lastId) as Difference, 
      @lastId := CAST(SUBSTRING(t.id,3) AS UNSIGNED) as dummy 
     from 
      `MyTable` t, 
      ( select @lastId := 0) SQLVars 
     order by 
      t.id 
) d 
WHERE diff>1; 

This is the inside query (not the final result set of the above)

+----------+--------+------+------------+-------+
| id       | s      | diff | Difference | dummy |
+----------+--------+------+------------+-------+
| AA000001 | 000001 |    1 |          0 |     1 |
| AA000002 | 000002 |    1 |          1 |     2 |
| AA000005 | 000005 |    3 |          3 |     5 |
| AA000008 | 000008 |    3 |          3 |     8 |
| AA000009 | 000009 |    1 |          1 |     9 |
| AA000010 | 000010 |    1 |          1 |    10 |
+----------+--------+------+------------+-------+

Actual Results of Above Query:

+----------+
| id       |
+----------+
| AA000005 |
| AA000008 |
+----------+

Here's the SQL Fiddle .

Answer 2

为了简单地测试是否有缺失值，

select count(*) <> max(right(col, 6))-min(right(col, 6))+1 || count(*) <> count(distinct col)