我有一个查询,例如:
SELECT COUNT(id) AS user_list FROM tbl_users
WHERE (enrolled = 1 AND age >=15 AND age < 20)
OR (enrolled = 1 AND age >=20 AND age < 25)
OR (enrolled = 1 AND age >=25 AND age < 30)
OR (enrolled = 1 AND age >=30)
如何让它为一行和一个表中的每个 where 条件返回结果:
user_list
---------
18 --(enrolled = 1 AND age >=15 AND age < 20)
12 --(enrolled = 1 AND age >=20 AND age < 25)
22 --(enrolled = 1 AND age >=25 AND age < 30)
56 --(enrolled = 1 AND age >=30)
最佳答案
正如已经提到的,您可以使用一个案例并在一个查询中执行这一切,但是您不需要使用子查询,尽管我不是它的忠实粉丝,MySQL 允许您在分组依据,因此以下内容将起作用:
SELECT CASE WHEN (enrolled = 1 AND age >=15 AND age < 20) THEN '15-19'
WHEN (enrolled = 1 AND age >=20 AND age < 25) THEN '20-24'
WHEN (enrolled = 1 AND age >=25 AND age < 30) THEN '25-29'
WHEN (enrolled = 1 AND age >=30) THEN '30+'
ELSE 'Other'
END AS AgeRange
COUNT(id) AS user_list
FROM tbl_users
WHERE Enrolled = 1
AND Age >= 15
GROUP BY AgeRange;
注意,我仍然添加了一个 where 子句以避免扫描冗余数据。
但是,如果您缺少数据,例如将返回一个空表,而不是这个:
AGERANGE USER_LIST
15-19 0
20-24 0
25-29 0
30+ 0
正如你所料。为了解决这个问题,我将创建一个伪表来选择,并左连接您的数据:
SELECT t.Name AS Age_Range,
COUNT(u.ID) AS User_List
FROM ( SELECT '15-19' AS Name, 15 AS LowerBound, 20 AS UpperBound, 1 AS Enrolled
UNION ALL
SELECT '20-24' AS Name, 20 AS LowerBound, 25 AS UpperBound, 1 AS Enrolled
UNION ALL
SELECT '25-29' AS Name, 25 AS LowerBound, 30 AS UpperBound, 1 AS Enrolled
UNION ALL
SELECT '30+' AS Name, 30 AS LowerBound, 9999999 AS UpperBound, 1 AS Enrolled
) t
LEFT JOIN tbl_Users u
ON u.Enrolled = t.enrolled
AND u.Age >= t.LowerBound
AND u.Age < t.UpperBound
GROUP BY t.Name;
关于php - 具有多个 where 子句的 select 查询是否在一个结果表中返回多个结果行?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19679375/