SELECT count (1)
    FROM table_a a
    FULL OUTER JOIN table_b b
        USING (<list of columns to compare>)
    WHERE a.id IS NULL
        OR b.id IS NULL ;

CREATE TABLE a (id int, val text);
INSERT INTO a VALUES (1, 'foo'), (2, 'bar');

CREATE TABLE b (id int, val text);
INSERT INTO b VALUES (1, 'foo'), (3, 'bar');

SELECT count (1)
    FROM a
    FULL OUTER JOIN b
        USING (id, val)
    WHERE a.id IS NULL
        OR b.id IS NULL ;

CREATE TABLE a (id int, val text);
INSERT INTO a VALUES (1, 'foo'), (2, 'bar');

CREATE TABLE b (id int, val text);
INSERT INTO b VALUES (1, 'foo'), (2, 'bar');

SELECT count (1)
    FROM a
    FULL OUTER JOIN b
        USING (id, val)
    WHERE a.id IS NULL
        OR b.id IS NULL ;

(TABLE a EXCEPT TABLE b)
UNION ALL
(TABLE b EXCEPT TABLE a) ;

SELECT CASE WHEN EXISTS (TABLE a EXCEPT TABLE b)
              OR EXISTS (TABLE b EXCEPT TABLE a)
            THEN 'different'
            ELSE 'same'
       END AS result ;

SELECT *
FROM a NATURAL FULL JOIN b
WHERE a.some_not_null_column IS NULL
   OR b.some_not_null_column IS NULL ;

SELECT CASE WHEN EXISTS
            ( SELECT *
              FROM a NATURAL FULL JOIN b
              WHERE a.some_not_null_column IS NULL
                 OR b.some_not_null_column IS NULL
            )
            THEN 'different'
            ELSE 'same'
       END AS result ;

SELECT * FROM first_table
EXCEPT
SELECT * FROM second_table

select count(*) from
(
select * From EmpDtl1
union
select * From EmpDtl2
)