如何在MySQL中任意绑定？

Question

我有一个表，其中有一列列出了用户的年龄。我想要在任意分组(13-17,18-25等)的仓位年龄，然后能够按这些仓位分组，并计算每个组中的用户。如何在查询中完成此操作？

Answer 1

SELECT CASE WHEN age BETWEEN 13 AND 17 THEN '13-17' 
            WHEN age BETWEEN 18 AND 25 THEN '18-25' 
            ELSE '26+' END AS AgeGroup,
    COUNT(*) AS total
FROM MyTable
GROUP BY AgeGroup

Answer 2

SELECT
  COUNT(CASE WHEN `age` BETWEEN 13 AND 17 THEN 1 END) `13-17`,
  COUNT(CASE WHEN `age` BETWEEN 18 AND 25 THEN 2 END) `18-25`,
  COUNT(CASE WHEN `age` > 25 THEN 3 END) `> 25`
FROM tableListOfAges;