父表中的 Select 记录取决于子表中的条件

Question

I have two tables: Order (parent) and Expedient (child)

Suppose this case:

Order
id |
order1 |

Expedient
id | order_id | status
1 | order1 | validated
2 | order1 | validated
3 | order1 | validated
4 | order1 | pending

I need a query that returns Order but only when the 4 child records are in state "validated"

If at least one of the records is in pending status, then no Order should be returned

I have tried with a subquery "NOT IN" excluding all pending expedients, but it's not working because always return me a Order

Answer 1

You could try using having count(status) >= 4

select  o.order_id 
from  `Order` o
INNER JOIN  Expedient e ON o.order_id = e.order_id
WHERE e.status = 'validated'
GROUP BY  o.order_id 
having count(e.status) >= 4

be careful using order as table name you need backtics..and should be better use another name.

and if you need also pendind = 0 then the having clause is

having count(e.status) >= 4 AND sum(status ='pending' )  =0

Answer 2

If all you need is the order's id then there is no need for a join:

select order_id
from Expedient
group by order_id
having sum(status = 'pending') = 0

I assume there are only the values 'validated' and 'pending' in the column status .
If you want exactly 4 rows with the value 'validated' in status :

select order_id
from Expedient
group by order_id
having sum(status = 'pending') = 0 and sum(status = 'validated') = 4

Answer 3

If at least one of the records is in pending status, then no Order should be returned

This is a case for a NOT EXISTS subquery:

select o.*
from `Order` o
where not exists (
  select *
  from Expedient e
  where e.order_id = o.id
    and e.status = 'pending'
)

An equivalent method is an "anti-join":

select o.*
from `Order` o
left join Expedient e
  on  e.order_id = o.id
  and e.status = 'pending'
where e.order_id is null

For both queries you should have an andex on Expedient(order_id, status [, other columns]) or Expedient(status, order_id, [, other columns]) .

A NOT IN query might also work:

select o.*
from `Order` o
where o.id not in (
  select e.order_id
  from Expedient e
  where e.status = 'pending'
)

But note, that it might return nothing, if Expedient.order_id can be NULL . For this query you should have an index on Expedient(status [, other columns]) - Ideally Expedient(status, order_id, [, other columns]) .