Question

I have two tables & data as below.

create table t1 (id int, name varchar(10));

create table t2 (id int, name varchar(10), t1id int);

insert into t1 values
(1,'value 1'),
(2,'value 2'),
(3,'value 3'),
(4,'value 3');

insert into t2 values
(1,'value 1',1),
(2,'value 2',1),
(3,'value 3',1),
(4,'value 3',2);

What I want is list of id from T1 (id) BUT NOT in T2 (t1id).

Output would be

3 , 4 as t1.id (3,4) are not present in T2 (t1id).

Raw Data

Answer 1

SELECT id
  FROM t1
 WHERE NOT EXISTS (SELECT NULL
                     FROM t2
                    WHERE t2.t1id = t1.id)