How to count occurences in comma separated column? - mysql

Question

Question table:
id | tags
--------------------------------------
1 | css,javascript,html
2 | mysql,sql,html
3 | css,spring,php
4 | css,java,html
I am trying to figure out how to return the number of times a string occurs in each of the tags's.
Result Table:
tags | count
--------------------------------------
css | 3
html | 3
javascript | 1
php | 1

Answer 1

You can use:
SqlFiddleDemo
SELECT sub.val AS tags, COUNT(*) AS `count`
FROM
(
SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(t.tags, ',', n.n), ',', -1) AS val
FROM tab 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.tags) - LENGTH(REPLACE(t.tags, ',', '')))
) sub
GROUP BY sub.val

Answer 2

You can simply try like this:
SELECT COUNT(*) FROM my_table WHERE tags like '%css%';
SELECT COUNT(*) FROM my_table WHERE tags like '%html%';
SELECT COUNT(*) FROM my_table WHERE tags like '%javascript%';
SELECT COUNT(*) FROM my_table WHERE tags like '%php%';
One other way is to use it like this:
(LENGTH(`tags`) - LENGTH(REPLACE(`tags`, 'searchword', '')))/LENGTH('searchword')