更有效的方式来运行日期/ yyyy查询？

Question

我使用以下查询相当多,但我很确定必须有一个更有效的方法来做到这一点.

基本上,我在用户表中计算人们出生的几十年:

select count(*) as howmany, yyyy from bday where (((yyyy > '1949')
AND (yyyy < '1961')) AND (user_id = '63')) UNION
select count(*) as howmany, yyyy from bday where (((yyyy > '1959')
AND (yyyy < '1971')) AND (user_id = '63')) UNION
select count(*) as howmany, yyyy from bday where (((yyyy > '1969')
AND (yyyy < '1981')) AND (user_id = '63')) UNION
select count(*) as howmany, yyyy from bday where (((yyyy > '1979')
AND (yyyy < '1991')) AND (user_id = '63')) UNION
select count(*) as howmany, yyyy from bday where (((yyyy > '1989')
AND (yyyy < '2001')) AND (user_id = '63'))

Answer 1

您可以计算十年并使用它来对用户进行分组:

SELECT
    COUNT(id) AS howmany,
    CEIL((`yyyy`+1)/10) AS decade,
    yyyy
FROM `bday`
GROUP BY decade