SQLite 3.8

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CREATE TABLE products
(
  year INTEGER
);
INSERT INTO products VALUES 
(2000),(2001),(2002),(2003),(2004),
(2005),(2006),(2007),(2008),(2009),
(2010),(2011),(2012),(2013),(2014); 
SELECT (year-(year%5))||'-'||(year-(year%5)+4) AS years
FROM products 
GROUP BY year-(year%5);


years


2000-2004

2005-2009

2010-2014


SELECT (CAST(year/5 AS INTEGER)*5)||'-'||MAX(year) AS years
FROM products 
GROUP BY CAST(year/5 AS INTEGER)*5;


years


2000-2004

2005-2009

2010-2014