MySQL - 检查不存在的记录

Question

I'm currently trying to check for existing rows in mysql.

I have a table called "history", in this table I save records of movements in my platform.

------------------------------------------------------------
| movement_id |     movement             |   product_id    |
------------------------------------------------------------
|  1          |       movement_1         |   5             |
------------------------------------------------------------
|  2          |       movement_2         |   5             |
------------------------------------------------------------
|  3          |       movement_3         |   5             |
------------------------------------------------------------
|  4          |       movement_1         |   6             |
------------------------------------------------------------
|  5          |       movement_3         |   6             |
------------------------------------------------------------

I would like to get all the product_id 's that don't have movement_2 but does have movement_3 . In the example above the ID that I would like to return is 6 , but this can be more than one id.

Any help is greatly appreciated: :)

Answer 1

You can group by product_id and use a condition in the having clause:

select product_id
from history
where movement in ('movement_2', 'movement_3')
group by product_id
having 
  sum(movement = 'movement_2') = 0
  and
  sum(movement = 'movement_3') > 0

or in this case only (because movement_2 < movement_3 ), this would work also:

having min(movement) = 'movement_3'

See the demo .
Results:

> | product_id |
> | ---------: |
> |          6 |