mysql 按照年齡段分組計數

最近在統計人羣特徵數據時，需要將用戶年齡分組來計數，mysql 裏的  case when  可以直接實現的  具體sql語句如下

SELECT
	age,
	count( * ) AS cnt 
FROM
	(
	SELECT
	CASE		
		WHEN info_t1 <= 20 THEN	'20' 
		WHEN info_t1 <= 30 AND info_t1 >= 21 THEN	'21-30' 
		WHEN info_t1 <= 40 AND info_t1 >= 31 THEN	'31-40' 
		WHEN info_t1 <= 50 AND info_t1 >= 41 THEN	'41-50' 
		WHEN info_t1 <= 60 AND info_t1 >= 51 THEN	'51-60' 
		WHEN info_t1 >= 61 THEN		'61' 
			END AS age 
		FROM
			`user_age` 
		) AS a 
GROUP BY
	age

結果如下圖：