SQL左连接带子句的右表

Question

I need to request customer on database with multiple criteria.

In my database, I have 3 tables

Customer :

id
nom
prenom
...

Contact :

id
valeur
customer_id

In my criteria of request, I have : valeur

This is the request :

select client0_.id as id1_6_
from client client0_ 
inner join entite entite1_ on client0_.entite_id=entite1_.id 
left outer join client_adresse clientadre2_ on     (clientadre2_.client_id=client0_.id) 
left outer join client_contact clientcont3_ on (clientcont3_.client_id=client0_.id) 
where (entite1_.numero_licence in ('ZB230EC')) 
and (upper(client0_.nom) like ('%'||upper('')||'%')) 
and (client0_.prenom is null or upper(client0_.prenom) like ('%'||upper('')||'%')) 
and (clientcont3_.valeur like ('%'||'@mail'||'%')) 
and (client0_.date_creation_sys is null or client0_.date_creation_sys>='2017-01-01') 
and (client0_.date_modification_sys is null or client0_.date_modification_sys>='2017-01-01') 
and (client0_.date_suppression is null or client0_.date_suppression>='9999-12-12')

This request return me customer which have not contact also my request ask customer with contact "valeur" contain "@mail"

Sample data

Customer

id  | nom     | prenom 
375 | aurelie |  lilie
389 | t(      | 

In Contact

id    |  valeur             | customer_id
2740  |  aurelie@mail.com   |  375
2739  |  06 06 06 06 06     |  375

If I launch request with search :

    contact.valeur like '%@mail%'
and customer.nom like '%%'

My result is OK

But with :

    contact.valeur like '%%'
and customer.nom like '%t(%'

I have empty result

Can you help me?

Answer 1

There are some pieces that explain this:

• First of all, you are doing a left join with these tables, so having or not data in the contact/address tables won't reduce the number of records in the output.
• If you were waiting to receive nothing because of the filters that you applied, you must know that the behaviour filtering a table in the join condition is not the same than filtering the table in the where condition:
  • Filter applied in a join: the filter is done before proceeding to join the tables
  • Filter applied in a where: the filter is done after joining the tables

Therefore, if you want to get nothing, just move your filter in the "join part" to the "where part".

Edited answer

Just to explain my comment...

with customer as (
  select 375 as id, 'aurelie' as nom, 'lilie' as prenom union all
  select 389, 't(', null
),
contact as (
  select 2740 as id, 'aurelie@mail.com' as valeur, 375 customer_id union all
  select 2739, '06 06 06 06 06', 375
)
select *
from customer cs
  left join contact c
    on cs.id=c.customer_id
where c.valeur like '%%'
  and cs.nom like '%t(%'

This return nothing, because you are comparing NULL with like '%%'

If you replace this where c.valeur like '%%' by this where c.valeur is null , you will get the record you are looking for. If you want to continue using this where c.valeur like '%%' always, you will need to convert the nulls to some string, for example an empty string where isnull(c.valeur,'') like '%%' and it should work too. Hope it helps, you can test it from here