PostgreSQL: Sort result by DateTime, but the null value should be first or last

I want to sort my result by date time column in ascending order but null values ​​should come first or vice versa. Suppose I have a table employee and it has the column appraisal_date if I sorted the result set by appraisal_date in ASC/DESC order it should be the null value come FIRST/LAST.

         

PostgreSQL provides keywords such as "NULLS FIRST | LAST" that help find accurate results with "ORDER BY CLAUSE."

Illustration to get the accurate result-set sort by DateTime in ascending (ASC) order but null first

First I will create an employee table

CREATE TABLE employee (        emp_id int generated always as identity,        name text,        appraisal_date date ); -- Here I will insert some records INSERT INTO employee ( name, appraisal_date)                      VALUES                      ('Dilip', '27/04/2020'),                      ('Mamta', '28/04/2020'),                      ('Ashish', null),                      ('Naina', '30/04/2020'),                      ('Aradhya', '21/04/2020'),                      ('Mukesh', null);

Sort Result null first

SELECT * FROM employee ORDER BY appraisal_date ASC NULLS FIRST;

Expected result

Illustration to get the accurate result-set sort by DateTime in descending (ASC) order but null first

SELECT * FROM employee ORDER BY appraisal_date DESC NULLS FIRST;

Expected Result

Illustration to get the accurate result-set sort by DateTime in descending (ASC) order but null first

SELECT * FROM employee ORDER BY appraisal_date ASC NULLS LAST;

Expected Result

Illustration to get the accurate result-set sort by DateTime in descending (ASC) order but null first

SELECT * FROM employee ORDER BY appraisal_date DESC NULLS LAST;

Expected Result

To support the query with an index, make it match:

CREATE INDEX appraisal_date_index ON employee (appraisal_date ASC NULLS FIRST);

OR

CREATE INDEX appraisal_date_index ON employee (appraisal_date DESC NULLS LAST);