Group rows by Year Band Interval

Question

I have a table (tbl_people), in this table I have a datetime field I want to group and count the records in groups of 10 years... The result should be something like:

Answer 1

This should work - SQL Fiddle (thanks to Olaf Dietsche for showing me that this wonderful site exists):

SELECT
    COUNT(`year`) as `count`,
    CONCAT(
        FLOOR(YEAR(`year`) / 10) * 10, 
        '-', 
        (CEIL(YEAR(`year`) / 10) * 10) - 1
    ) as `year`
FROM
    `tbl_people`
GROUP BY
    CONCAT(
        FLOOR(YEAR(`year`) / 10) * 10,
        '-', 
        (CEIL(YEAR(`year`) / 10) * 10) - 1
    )

If the number is 1992, FLOOR(1992 / 10) will give 199, and times with 10 will give 1990. The same thing about CEIL(1992 / 10) = 200 and times 10 = 2000, minus 1, gives 1999 so the year should be 1990-1999.