将2个SQL查询合并为一个

Question

I spent many hours combining my query into one. I have 3 database table. This is example schema.

I have only user name from session. I need take all tickets from database from user company.
Example:
User A working in company B.
Company B have many workers. Workers creating tickets.
User A after login see all tickets from yours company.
I now done this using 2 query:
- Take usera A company id
- Take tickets where users work in specifist company.

Answer 1

This should do it:

SELECT *
FROM User u1 
INNER JOIN User u2 on u2.id_company = u1.id_company
INNER JOIN Ticket t on t.id_author = u2.id_user
WHERE u1.Name = @SessionUser

Answer 2

Is this what you are looking for?

select t.*
from users u join
     tickets t
     on u.id_user = t.id_author
where u.company_id = (select u2.company_id from users u2 where u2.id_user = 'UserA');

Answer 3

Joins are typically faster than subqueries, however a lot of DBMS' optimize subqueries into joins, so the difference between the queries is probably not important. Below is a reworked version of Gordon Linoff's query removing the subquery.

   select t.* from Users u1 
   join User u2 on u2.id_company = u1.id_company
   join Ticket t on t.id_author = u1.id_user
   where u1.id.user = 'User1';

However again, if your database optimizes the SQL the difference is negligible.