SQL Count Distinct?

Question

I have a table that is laid out as below:

id - tag_id - post_id
1  -    1   -  3
2  -    1   -  6
3  -    1   -  2
4  -    2   -  3
5  -    2   -  9
6  -    1   -  7

I would like to write an mySQL statement that finds out how many times a tag is referenced.

I would then use PHP to format the results. tag # was referenced # times and they would be sorted in order of # times .

My ability with MySQL is limited to very basic SELECT, INSERT, UPDATE and DELETE statements, so I'm not sure of the way to go about this. Can you help?

Answer 1

select tag_id, count(*)
from mytable
group by tag_id
order by count(*) desc

This will order your results by count(*) in descending order, meaning the tags with most posts will appear on top rows.

Answer 2

SELECT tag_id, COUNT(*) FROM table GROUP BY tag_id将为您提供每个标签id的计数

Answer 3

To get the tags and the number of posts each tag has, sorted in descending order, you could use the following query :

select tag_id, count(*) as num
from your_table
group by tag_id
order by count(*) desc

(Of course, if you want the same data, but sorted in ascending order, just remove the desc in the order by clause)