Integrating COUNT() into a nested MySQL query-CodePudding

I have the following nested MYSQL query. Currently, out of the results, I go through and tally the tag appearances to identify the frequency. I've tried to integrate MYSQL's COUNT() into my query but have been unable to.

Current query:

SELECT tagId 
FROM refTags 
WHERE postId IN (SELECT postId FROM refTags WHERE tagId = 1) 
AND tagId <> 1
ORDER BY tagId ASC

The desired return is tagId, COUNT(tagId) sorted by COUNT(tagId) DESC.

Am I able to do this all in the same query or am I correct in doing the counting after the results return?

CodePudding user response：

You want one result row per tag ID, so group by tag ID. Then count.

SELECT tagId, COUNT(*) AS number_of_posts
FROM refTags 
WHERE postId IN (SELECT postId FROM refTags WHERE tagId = 1)
AND tagId <> 1 
GROUP BY tagId
ORDER BY COUNT(*) DESC;