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，我指望的人出生在几十年中，从用户表内：

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

就可以计算出十年并用它来组的用户：

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

Answer 2

到算出几十年出生的人：

select substring(yyyy, 1, 3) || '0''s' decade, count(*) howmany 
from bday 
group by decade