One algorithm to determine if a year is a Common or a Leap Year is:
if (year is not divisible by 4) then (it is a common year)
else if (year is not divisible by 100) then (it is a leap year)
else if (year is not divisible by 400) then (it is a common year)
else (it is a leap year)
I’d like to create a user-defined SQL function in Vertica that will let me know if the year of the date I pass in is a Leap Year. I could try and create a function that has a complex SQL CASE statement to apply the above algorithm, but it’s a lot easier to simply use the Vertica LAST_DAY function.Example:
dbadmin=> CREATE OR REPLACE FUNCTION is_leap_year (x DATE) RETURN BOOLEAN
dbadmin-> AS
dbadmin-> BEGIN
dbadmin-> RETURN EXTRACT(DAY FROM LAST_DAY(('02/01/' || EXTRACT(YEAR FROM X))::DATE)) = 29;
dbadmin->
dbadmin-> END;
CREATE FUNCTION
dbadmin=> SELECT is_leap_year(SYSDATE::DATE);
is_leap_year
--------------
f
(1 row)
dbadmin=> SELECT is_leap_year('01/01/2000'::DATE);
is_leap_year
--------------
t
(1 row)
dbadmin=> SELECT is_leap_year('01/01/1800'::DATE);
is_leap_year
--------------
f
(1 row)
dbadmin=> SELECT is_leap_year('01/01/2020'::DATE);
is_leap_year
--------------
t
(1 row)
Helpful Links:https://www.vertica.com/docs/latest/HTML/Content/Authoring/SQLReferenceManual/Functions/Date-Time/LAST_DAY.htm https://en.wikipedia.org/wiki/Leap_year
Have fun!
About the Author
James Knicely
Vertica Field Chief Technologist
I've had the privilege of working with many database technologies in my career. But after being introduced to Vertica in May of 2011 as a client, I was hooked on the new technology after witnessing a query run in milliseconds that had previously ran for hours on the legacy database we had in place. It was then that I knew I wanted to eventually join the Vertica team, and 4 years later I did! I am currently a Vertica evangelist and am ready to help you get on board! Please feel free to reach out to me with any questions you have about Vertica and make sure to follow my Vertica Quick Tips!
