Adding Or Substracting Time

Create Table

-- Create table called dead_adventurers
CREATE TABLE dead_adventurers (
    -- string variable
    name varchar(255),
    -- integer variable
    age int,
    -- string variable
    race varchar(255),
    -- string variable
    weapon varchar(255),
    -- date variable
    died date
)

Insert Rows

-- Insert into the table dead_adventurers
INSERT INTO dead_adventurers (name, age, race, weapon, died)
VALUES ('Fjoak Doom-Wife', 28, 'Human', 'Axe', '09-Nov-2017'),
       ('Alooneric Cortte', 29, 'Elf', 'Bow', '10-JAN-2017'),
       ('Piperel Ramsay', 35, 'Elf', 'Sword', '12-APR-2016'),
       ('Casimir Yardley', 14, 'Elf', 'Magic', '06-MAY-2017')

Create New Column Three Days Later

-- Create a column called three_days_laters that takes the value
-- of died and adds three days to it
SELECT died + INTERVAL '3 day' AS three_days_later
-- From adventurers table
FROM dead_adventurers
three_days_later
2017-11-12 00:00:00.000000
2017-01-13 00:00:00.000000
2016-04-15 00:00:00.000000
2017-05-09 00:00:00.000000

Create New Column Two Months Before

-- Create a column called two_months_later that takes the value
-- of died and subtracts two months to it
SELECT died - INTERVAL '2 month' AS one_months_later
-- From adventurers table
FROM dead_adventurers
three_days_later
2017-11-12 00:00:00.000000
2017-01-13 00:00:00.000000
2016-04-15 00:00:00.000000
2017-05-09 00:00:00.000000