Discriminate data from functions aggregate on PosgreSQL - sql

Question

On PosgreSQL I have a database of pizza restaurant.
With this code:
SELECT command.id_command, array_agg(history_state_of_command.state)
FROM command JOIN history_state_of_command
ON command.id_command = history_state_of_command.id_command
GROUP BY command.id_command
I obtain these results, with the id of a command and the associated state of command:
command.id_command State of command
1
"{Pizza_Order,Pizza_in_preparation,Pizza_prepared,Pizza_ready_for_delivery,Pizza_delivering,Pizza_deliver}"
2
"{Pizza_Order,Pizza_in_preparation}"
3
"{Pizza_Order,Pizza_in_preparation,Pizza_prepared,Pizza_ready_for_delivery,Pizza_delivering,Pizza_deliver,"Command cancelled"}"
4
"{Pizza_Order,Pizza_in_preparation,Pizza_prepared,Pizza_ready_for_delivery,Pizza_delivering,Pizza_deliver}"
I would like to find an SQL code where I obtain only id of command where the pizza was never prepared:
command.id_command State of command
2 "{Pizza_Order,Pizza_in_preparation}"
Many thanks for your help !

Answer 1

You can use a correlated subquery to find this command:
select h.id_command
from history_state_of_command h
where h.state in ('Pizza_Order', 'Pizza_in_preparation')
and not exists (
select 1
from history_state_of_command i
where i.id_command = h.id_command and i.state = 'Pizza_prepared'
)

Answer 2

You can use aggregation as well:
select hsc.id_command
from history_state_of_command hsc
group by hsc.id_command
having count(*) filter (where hsc.state = 'Pizza_prepared') = 0;
Note: This assumes that commands have some row in the history. If not, then use not exists;
select c.*
from command c
where not exists (select 1
from history_state_of_command hsc
where hsc.id_command = c.id_command and hsc.state = 'Pizza_prepared'
);
This is probably the most efficient method, with appropriate indexes.