带计数的交叉联接MySQL查询

Question

I need some help with a MySQL query. I have a table with two columns (usr_id and search_term) and with the following data.

1 term1
1 term2
2 term1
2 term2
2 term3
3 term2
3 term3
4 term1
4 term3

I need to be write a query to generate the a list of all the possible combinations of terms and report the total number of usr_id's where the combination occurs.

term1 term2 2
term1 term3 1
term2 term3 1

Answer 1

If I understand correctly, you want to count the number users that have any given pair of terms. You have to be careful about not overcounting if a user uses a term more than once.

select t1.term as term1, t2.term as term2,
       count(distinct t1.usr_id) as num_users
from table t1 join
     table t2
     on t1.usr_id = t2.usr_id and t1.term <> t2.term
group by t1.term, t2.term;