How to make an exact match between Ids with one column in common? - sql

Question

I must confess I have no idea into to how properly ask this question but I'll try to do my best.
I have two tables (PROMO and DETAILED_PROMO) that are related by a forkeign key (ID_PROMO). The tables are as follow:
PROMO
--ID_PROMO
--DESCRIPTION
DETAILED_PROMO
--ID_DETAILED_PROMO
--ID_PROMO
--ID_SERVICE
When I create a new promo in the table PROMO it also creates one or several registers in the table DETAILED_PROMO with the different services associated to that promo. Something like this:
--------PROMO----------
ID_PROMO | DESCRIPTION
------------------------
id_promo1 | Promo 1
----------|-------------
id_promo2 | Promo 2
----------| ------------
id_promo3 | Promo 3
-----------DETAILED PROMO----------------------
ID_DETAILED_PROMO | ID_PROMO| ID_SERVICE
-------------------|---------|-----------------
id_detailed_promo1 |id_promo1| Id_Service1
-------------------|---------|-----------------
id_detailed_promo2 |id_promo1| Id_Service2
-------------------|---------|-----------------
id_detailed_promo3 |id_promo1| Id_Service3
-------------------|---------|-----------------
id_detailed_promo4 |id_promo2| Id_Service1
-------------------|---------|-----------------
id_detailed_promo5 |id_promo2| Id_Service2
-------------------|---------|-----------------
id_detailed_promo6 |id_promo2| Id_Service4
-------------------|---------|-----------------
id_detailed_promo7 |id_promo3| Id_Service1
-------------------|---------|-----------------
id_detailed_promo7 |id_promo3| Id_Service2
-------------------|---------|-----------------
id_detailed_promo7 |id_promo3| Id_Service3
-------------------|---------|-----------------
id_detailed_promo7 |id_promo3| Id_Service4
The rules of creating or updating a promo is that there cannot exist another promo with the exact numbers of services and the same Id_Service.
For example, if I try to delete from DETAILED_PROMO the Id_Service 4 from id_promo3, the Promo 3 would have the same numbers of services AND the same services of Promo 1 therefore deleting that Id_Service should not be allowed. If I delete Id_Service3 from id_promo3, the Promo 3 would have the same numbers of services AND the same services of Promo 2. BUT if I delete Id_Service1 from id_promo3, no other promos have the same services and the same number of services associated to it, so it should allow me to delete that register.
How can I validate this? If I want to delete a register, I am being given the ID_DETALED_PROMO and the ID_PROMO as parameters in the store procedure.

Answer 1

I think here is what you can do for checking , I used int for ids:
this query checks if there is the same number of serviceids with similar ids in each promo :
DECLARE #ID_promo INT = 3;
DECLARE #Id_Service INT = 4;
SELECT
d1.ID_promo
, COUNT(CASE WHEN d1.ID_Service = d2.ID_Service THEN 1 ELSE NULL END) equalcount
, COUNT(d1.id) totalcount
FROM
detailed_promo d1
LEFT JOIN detailed_promo d2
ON d1.id_Service = d2.Id_service
AND d2.ID_Service NOT IN (#Id_Service)
AND d2.ID_PROMO = #ID_promo
WHERE
d1.id_promo <> #ID_promo
GROUP BY
d1.ID_promo
HAVING
COUNT(CASE WHEN d1.ID_Service = d2.ID_Service THEN 1 ELSE NULL END) = COUNT(d1.id);
so If you want to to delete check you can do something like this
delete from detailed_promo where id = #ID_promo and id_service= #Id_Service and not exists (queryabove)
you also can use multiple serviceIds if you are deleting multiple service ids within one promo id
and If I'm not mistaken the same rule applies for insert and update, so the same query can be used for Insert/Update as well.