SQL Server Left Join Counting - sql

Question

I got this sample code
create table #Reservation
(id int identity(1,1),
name varchar(50)
);
create table #Reservation_details
(id int identity(1,1),
reservation_id int,
reservation_date date,
seated tinyint
);
create table #Payment
(id int identity(1,1),
reservation_id int,
payment decimal(18,2)
);
insert into #Reservation(name)
values ('Spiderman'),('Superman'),('Batman'),('Hulk');
insert into #Reservation_details(reservation_id,reservation_date,seated)
values (1,'2017-12-07',0),(2,'2017-12-08',0),(3,'2017-12-08',1),(4,'2017-12-08',0);
insert into #Payment(reservation_id,payment)
values(1,220),(2,1000)
select
A.id,
A.name,
B.reservation_date,
B.seated,
C.payment
from #Reservation A
inner join #Reservation_details B
on B.reservation_id = A.id
left join #Payment C
on C.reservation_id = B.reservation_id
where reservation_date = '2017-12-08'
drop table #Reservation
drop table #Reservation_details
drop table #Payment
I wanted to get the count of all reservations where date is '2017-12-08' and seated = 1 or payment is not null
I've tried putting where date is '2017-12-08' and seated = 1 or payment is not
null
but instead it showed me the past date also how do use where as count?

Answer 1

Try it
select COUNT(*)
from #Reservation A
inner join #Reservation_details B on B.reservation_id = A.id
left join #Payment C on C.reservation_id = B.reservation_id
where reservation_date = '2017-12-08'
and (B.seated=1 or C.payment is not null)
I think you forgot to use brackets (condition1 OR condition2) for OR operation.
See operator precedence - https://learn.microsoft.com/en-us/sql/t-sql/language-elements/operator-precedence-transact-sql
In your case if you don't use brackets then
reservation_date = '2017-12-08' and B.seated=1 or C.payment is not null
equals the following
(reservation_date = '2017-12-08' and B.seated=1) or C.payment is not null

Answer 2

select
A.id,
A.name,
B.reservation_date,
B.seated,
C.payment
from (#Reservation A
inner join #Reservation_details B
on B.reservation_id = A.id
left join #Payment C
on C.reservation_id = B.reservation_id)
where B.reservation_date = '2017-12-08'
AND (B.seated =1 or C.payment is null)
You can use COUNT function by using HAVING in WHERE clause , it should be last statement and after the GROUP BY clause