MYSQL选择逗号分隔的不同值的计数
如何从MySql中以逗号分隔的值存储的数据中选择不同的值和相对计数 表中的数据如下所示:MYSQL选择逗号分隔的不同值的计数,mysql,Mysql,如何从MySql中以逗号分隔的值存储的数据中选择不同的值和相对计数 表中的数据如下所示: "Category" "Values" "red" "D,A,D,D" "yellow" "A,A,D,D" 期望输出: "red" "D" "3" "red" "A" "1" "yellow" "D" "2" "yellow" "A" "2" 你能想出一个在mysql中像我这样获得输出的好方法吗? 提前感谢。使用派生表
"Category" "Values"
"red" "D,A,D,D"
"yellow" "A,A,D,D"
期望输出:
"red" "D" "3"
"red" "A" "1"
"yellow" "D" "2"
"yellow" "A" "2"
你能想出一个在mysql中像我这样获得输出的好方法吗?
提前感谢。使用派生表可以将字符串拆分为行
SELECT `Category`, SUBSTRING_INDEX(SUBSTRING_INDEX(t.`Values`, ',', n.n), ',', -1) `value`
FROM table1 t CROSS JOIN
(
SELECT a.N + b.N * 10 + 1 n
FROM
(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) a
,(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) b
ORDER BY n
) n
WHERE n.n <= 1 + (LENGTH(t.`Values`) - LENGTH(REPLACE(t.`Values`, ',', '')))
是的,我能想到的一个好方法是对表格进行规范化,使其成为一对多,之后的生活将变得简单。只要您知道可能值的上限,这将很有效,在本例中为9。很好的解决方案。
SELECT `Category`, `value`, COUNT(*) as cnt
FROM (
<previous query>
) T
GROUP BY `Category`, `value`