Is This Year a Leap Year? A SQL Solution

Building Logic In SQL

2 min readJun 8, 2024

Hello Everyone,

I have been working with SQL since the beginning of my backend journey, so I decided to improve both my and your SQL skills by solving simple problems, just as we used to do when learning programming languages like Python and others.

I will use small SQL snippets, run them to show you the output, and then combine all parts to create a complete solution.

Step 1 -> Extracting Current Year

select date_trunc('year',current_date)::date;

2024-01-01

Step 2 -> Extract First Date of Feb and March

select
 (date_trunc('year',current_date) + interval '2 month')::date as march_date,
 (date_trunc('year',current_date) + interval '1 month')::date as feb_date;

 march_date |  feb_date  
------------+------------
 2024-03-01 | 2024-02-01

Step 3 -> Substract Feb 1 from March 1 to get Interval of Days

select march_date - feb_date as days from (
 select
  (date_trunc('year',current_date) + interval '2 month')::date as march_date,
  (date_trunc('year',current_date) + interval '1 month')::date as feb_date
)X ;

 days 
------
   29

Step 4-> Use Case When to decide Leap Or Not.

select case 
 when ( march_date - feb_date ) = 29
 then 'Leap Year'
 else 'Non Leap Year'
end from (
 select
  (date_trunc('year',current_date) + interval '2 month')::date as march_date,
  (date_trunc('year',current_date) + interval '1 month')::date as feb_date
)X ;

Leap Year

Conclusion

In this exercise, we’ve demonstrated how to determine if the current year is a leap year using a series of SQL queries. By breaking down the problem into smaller steps, we were able to: