In this post, I am sharing a simple way to get the data difference between two tables in PostgreSQL.

Recently, one of the junior folk asked me about this and I prepared the query using FULL OUTER JOIN.

Using this solution, you can get the missing data for both tables in the form of differences.

Create two sample tables:

CREATE TABLE tbl_A
(ID INT);

CREATE TABLE tbl_B
(ID INT);

Insert sample data into both tables:

INSERT INTO tbl_A
VALUES
(1),(2),(3);

INSERT INTO tbl_B
VALUES
(1),(4),(5);

Check the difference of data:

SELECT 
	a.id as tbl_B_Missing
	,b.id as tbl_A_Missing
FROM tbl_A a
FULL OUTER JOIN tbl_B b 
	ON a.ID = b.ID
WHERE a.ID IS NULL OR b.ID IS NULL

Result:

tbl_b_missing   |   tbl_a_missing
---------------------------------
       2        |     [null]
       3        |     [null] 
     [null]     |       4
     [null]     |       5