一起使用DISTINCT和COUNT

Question

I have two different product_id with multiple keywords per each. Following statement is not working:

SELECT distinct product_id, COUNT(distinct keyword) as keyword_sum FROM data;

Currently result looks like this:

product_id     keyword_sum
2              47

Desired result would look like this:

product_id     keyword_sum
2              26
3              21

Any help much appreciated!

Answer 1

Group by the column you want to be unique and then you can use aggregate functions like count on each element of the group.

SELECT product_id, COUNT(distinct keyword) as keyword_sum 
FROM data
GROUP BY product_id