MySQL GROUP BY年龄范围包括空范围

Question

我正在尝试按年龄范围计算人数,我几乎可以解决2个问题:

1. 如果在给定年龄范围内没有人(NULL),则该年龄范围不会出现在结果中.例如,在我的数据中没有"超过80"的条目,因此不会出现日期范围.基本上,当缺少日期范围时,它看起来像编程中的错误.

2. 我想以特定的方式订购结果.在下面的查询中,因为ORDER BY是age_range,'20 - 29'的结果出现在'20岁以下'的结果之前.

这是db表"查询"的示例:

inquiry_id  birth_date
1           1960-02-01
2           1962-03-04
3           1970-03-08
4           1980-03-02
5           1990-02-08

这是查询:

SELECT
    CASE
        WHEN age < 20 THEN 'Under 20'
        WHEN age BETWEEN 20 and 29 THEN '20 - 29'
        WHEN age BETWEEN 30 and 39 THEN '30 - 39'
        WHEN age BETWEEN 40 and 49 THEN '40 - 49'
        WHEN age BETWEEN 50 and 59 THEN '50 - 59'
        WHEN age BETWEEN 60 and 69 THEN '60 - 69'
        WHEN age BETWEEN 70 and 79 THEN '70 - 79'
        WHEN age >= 80 THEN 'Over 80'
        WHEN age IS NULL THEN 'Not Filled In (NULL)'
    END as age_range,
    COUNT(*) AS count

    FROM (SELECT TIMESTAMPDIFF(YEAR, birth_date, CURDATE()) AS age FROM inquiries) as derived

    GROUP BY age_range

    ORDER BY age_range

这是一个基于Wrikken建议的简单解决方案:

SELECT
    SUM(IF(age < 20,1,0)) as 'Under 20',
    SUM(IF(age BETWEEN 20 and 29,1,0)) as '20 - 29',
    SUM(IF(age BETWEEN 30 and 39,1,0)) as '30 - 39',
    SUM(IF(age BETWEEN 40 and 49,1,0)) as '40 - 49',
    SUM(IF(age BETWEEN 50 and 59,1,0)) as '50 - 59',
    SUM(IF(age BETWEEN 60 and 69,1,0)) as '60 - 69',
    SUM(IF(age BETWEEN 70 and 79,1,0)) as '70 - 79',
    SUM(IF(age >=80, 1, 0)) as 'Over 80',
    SUM(IF(age IS NULL, 1, 0)) as 'Not Filled In (NULL)'

FROM (SELECT TIMESTAMPDIFF(YEAR, birth_date, CURDATE()) AS age FROM inquiries) as derived

Answer 1

范围表的替代(有我的偏好),单行答案可以是:

SELECT
    SUM(IF(age < 20,1,0)) as 'Under 20',
    SUM(IF(age BETWEEN 20 and 29,1,0)) as '20 - 29',
    SUM(IF(age BETWEEN 30 and 39,1,0)) as '30 - 39',
    SUM(IF(age BETWEEN 40 and 49,1,0)) as '40 - 49',
...etc.
FROM inquiries;

Answer 2

对结果进行排序的一种方法是在 select 语句中引入一列，并为其指定您希望结果与其余部分一起排序的方式的排名值，然后按该行排序，例如

SELECT
CASE
    WHEN age < 20 THEN 'Under 20'
    WHEN age BETWEEN 20 and 29 THEN '20 - 29'
    WHEN age BETWEEN 30 and 39 THEN '30 - 39'
    WHEN age BETWEEN 40 and 49 THEN '40 - 49'
    WHEN age BETWEEN 50 and 59 THEN '50 - 59'
    WHEN age BETWEEN 60 and 69 THEN '60 - 69'
    WHEN age BETWEEN 70 and 79 THEN '70 - 79'
    WHEN age >= 80 THEN 'Over 80'
    WHEN age IS NULL THEN 'Not Filled In (NULL)'
END as age_range,
COUNT(*) AS count,
 CASE
    WHEN age < 20 THEN 1
    WHEN age BETWEEN 20 and 29 THEN 2
    WHEN age BETWEEN 30 and 39 THEN 3
    WHEN age BETWEEN 40 and 49 THEN 4
    WHEN age BETWEEN 50 and 59 THEN 5
    WHEN age BETWEEN 60 and 69 THEN 6
    WHEN age BETWEEN 70 and 79 THEN 7
    WHEN age >= 80 THEN 8
    WHEN age IS NULL THEN 9
END as ordinal

FROM (SELECT TIMESTAMPDIFF(YEAR, birth_date, CURDATE()) AS age FROM inquiries) as derived

GROUP BY age_range

ORDER BY ordinal