SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id

SELECT * FROM t1
  LEFT JOIN t2 ON t1.id = t2.id
  UNION ALL
  SELECT * FROM t1
  RIGHT JOIN t2 ON t1.id = t2.id
  WHERE t1.id IS NULL

-- t1
id  name
1   Tim
2   Marta

-- t2
id  name
1   Tim
3   Katarina

SELECT *
FROM `t1`
INNER JOIN `t2` ON `t1`.`id` = `t2`.`id`;

1 Tim  1 Tim

SELECT *
FROM `t1`
LEFT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`;

1 Tim   1    Tim
2 Marta NULL NULL

SELECT *
FROM `t1`
RIGHT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`;

1    Tim   1  Tim
NULL NULL  3  Katarina

1    Tim   1    Tim
2    Marta NULL NULL
NULL NULL  3    Katarina

SELECT *
FROM `t1`
LEFT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`

UNION

SELECT *
FROM `t1`
RIGHT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`;

SELECT *
FROM `t1`
LEFT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`

UNION

SELECT *
FROM `t1`
RIGHT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`
WHERE `t1`.`id` IS NULL;

[Table: t1]                            [Table: t2]
value                                  value
-------                                -------
1                                      1
2                                      2
4                                      2
4                                      5

value | value
------+-------
1     | 1
2     | 2
2     | 2
Null  | 5
4     | Null
4     | Null

value | value
------+-------
Null  | 5
1     | 1
2     | 2
4     | Null

select
    t1.value, t2.value
from t1
left outer join t2
  on t1.value = t2.value
union all      -- Using `union all` instead of `union`
select
    t1.value, t2.value
from t2
left outer join t1
  on t1.value = t2.value
where
    t1.value IS NULL

value | value
------+-------
1     | 1
2     | 2
2     | 2
4     | NULL
4     | NULL
NULL  | 5

-- (t1 ∩ t2): all in both t1 and t2
select t1.value, t2.value
from t1 join t2 on t1.value = t2.value
union all  -- And plus
-- all in t1 that not exists in t2
select t1.value, null
from t1
where not exists( select 1 from t2 where t2.value = t1.value)
union all  -- and plus
-- all in t2 that not exists in t1
select null, t2.value
from t2
where not exists( select 1 from t1 where t2.value = t1.value)

SELECT *
FROM leftTable lt
LEFT JOIN rightTable rt ON lt.id = rt.lrid
UNION
SELECT lt.*, rl.*  -- To match column set
FROM rightTable rt
LEFT JOIN  leftTable lt ON lt.id = rt.lrid

-- t1 left join t2
SELECT t1.value, t2.value
FROM t1 LEFT JOIN t2 ON t1.value = t2.value

    UNION ALL -- include duplicates

-- t1 right exclude join t2 (records found only in t2)
SELECT t1.value, t2.value
FROM t1 RIGHT JOIN t2 ON t1.value = t2.value
WHERE t2.value IS NULL

SELECT * FROM t1 FULL OUTER JOIN t2 ON t1.Name = t2.Name;

SELECT t1.*, t2.*
FROM (SELECT name FROM t1 UNION  -- This is intentionally UNION to remove duplicates
      SELECT name FROM t2
     ) n LEFT JOIN
     t1
     ON t1.name = n.name LEFT JOIN
     t2
     ON t2.name = n.name;

SELECT
    a.name,
    b.title
FROM
    author AS a
LEFT JOIN
    book AS b
    ON a.id = b.author_id
UNION
SELECT
    a.name,
    b.title
FROM
    author AS a
RIGHT JOIN
    book AS b
    ON a.id = b.author_id

SELECT t1.*, t2.*
FROM table1 t1
INNER JOIN table2 t2
ON 1=1;

SELECT t1.name, t2.name FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT t1.name, t2.name FROM t2
LEFT JOIN t1 ON t1.id = t2.id

SELECT * FROM students
LEFT JOIN marks
ON students.id = marks.id
UNION ALL
SELECT * FROM students
RIGHT JOIN marks
ON students.id = marks.id;

(
    SELECT a.* FROM tablea a
    LEFT JOIN tableb b ON a.`key` = b.key
    WHERE b.`key` is null
    )
    UNION ALL
    (
    SELECT a.* FROM tablea a
    LEFT JOIN tableb b ON a.`key` = b.key
    where  a.`key` = b.`key`
    )
    UNION ALL
    (
    SELECT b.* FROM tablea a
    right JOIN tableb b ON b.`key` = a.key
    WHERE a.`key` is null
    );

SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id

SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t2
LEFT JOIN t1 ON t2.id = t1.id

SELECT * FROM t1 FULL OUTER JOIN t2 ON t1.id = t2.id;

SELECT t1.*, t2.*
 FROM (SELECT * FROM t1 UNION SELECT name FROM t2) tmp
 LEFT JOIN t1 ON t1.id = tmp.id
 LEFT JOIN t2 ON t2.id = tmp.id;

WITH cte_t1 AS
 (
       SELECT 1 AS id1
       UNION ALL SELECT 2
       UNION ALL SELECT 5
       UNION ALL SELECT 6
       UNION ALL SELECT 6
 ),
cte_t2 AS
(
      SELECT 3 AS id2
      UNION ALL SELECT 4
      UNION ALL SELECT 5
      UNION ALL SELECT 6
      UNION ALL SELECT 6
)
SELECT  *  FROM  cte_t1 t1 FULL OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2;

This gives us this answer:

id1  id2
1  NULL
2  NULL
NULL  3
NULL  4
5  5
6  6
6  6
6  6
6  6

SELECT  * FROM  cte_t1 t1 LEFT OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2
UNION
SELECT  * FROM cte_t1 t1 RIGHT OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2

id1  id2
NULL  3
NULL  4
1  NULL
2  NULL
5  5
6  6

SELECT  * FROM cte_t1 t1 LEFT OUTER join cte_t2 t2 ON t1.id1 = t2.id2
UNION ALL
SELECT  * FROM  cte_t1 t1 RIGHT OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2

id1  id2
1  NULL
2  NULL
5  5
6  6
6  6
6  6
6  6
NULL  3
NULL  4
5  5
6  6
6  6
6  6
6  6

SELECT t1.*, t2.*
FROM (SELECT * FROM t1 UNION SELECT name FROM t2) tmp
LEFT JOIN t1 ON t1.id = tmp.id
LEFT JOIN t2 ON t2.id = tmp.id;

id1  id2
1  NULL
2  NULL
NULL  3
NULL  4
5  5
6  6
6  6
6  6
6  6