how to select set of records is ID is present in one of them - sql

Question

Here is the table where ORGID/USERID makes unique combination:
ORGID USERID
1 1
1 2
1 3
1 4
2 1
2 5
2 6
2 7
3 9
3 10
3 11
I need to select all records (organizations and users) wherever USERID 1 is present. So USERID=1 is present in ORGID 1 and 2 so then select all users for these organizations including user 1 itself, i.e.
ORGID USERID
1 1
1 2
1 3
1 4
2 1
2 5
2 6
2 7
Is it possible to do it with one SQL query rather than SELECT *.. WHERE USERID IN (SELECT...

Answer 1

You could use exists:
select *
from mytable t
where exists (select 1 from mytable t1 where t1.orgid = t.orgid and t1.userid = 1)
Another option is window functions. In Postgres:
select *
from (
select t.*,
bool_or(userid = 1) over(partition by orgid) has_user_1
from mytable t
) t
where has_user_1
Or a more generic approach, that uses portable expressions:
select *
from (
select t.*,
max(case when userid = 1 then 1 else 0 end) over(partition by orgid) has_user_1
from mytable t
) t
where has_user_1 = 1

Answer 2

Yes, you can do it with a single select statement - no in or exists conditions, no analytic or aggregate functions in a subquery, etc. Why you want to do it that way is not clear; in any case, it is possible that the solution below is also more efficient than the alternatives. You will have to test on your real-life data to see if that is true.
The solution below has two potential disadvantages: it only works in Oracle (it uses a proprietary extension of SQL, the match_recognize clause); and it only works in Oracle 12.1 or higher.
with
my_table(orgid, userid) as (
select 1, 1 from dual union all
select 1, 2 from dual union all
select 1, 3 from dual union all
select 1, 4 from dual union all
select 2, 1 from dual union all
select 2, 5 from dual union all
select 2, 6 from dual union all
select 2, 7 from dual union all
select 3, 9 from dual union all
select 3, 10 from dual union all
select 3, 11 from dual
)
-- End of SIMULATED data (for testing), not part of the solution.
-- In real life you don't need the WITH clause; reference your actual table.
select *
from my_table
match_recognize(
partition by orgid
all rows per match
pattern (x* a x*)
define a as userid = 1
);
Output:
ORGID USERID
---------- ----------
1 1
1 2
1 3
1 4
2 1
2 5
2 7
2 6

Answer 3

You can use exists:
select ou.*
from orguser ou
where exists (select 1
from orguser ou ou2
where ou2.orgid = ou.orgid and ou2.userid = 1
);

Answer 4

Apart from Exists and windows function, you can use IN as follows:
select *
from your_table t
where t.orgid in (select t1.orgid from your_table t1 where t1.userid = 1)