根据主键表的主键获取外键表的行数

Question

As usual in PK and Fk relationship.

I am having two tables one is lets say items_info and second is poll_report

items_info structure is as follows

 _id       Autogenerated integer based PK

Question   varchar(255) 

poll_report

_id       Autogenerated integer based PK

questionId FK to prev table's _id

answerId  integer

deviceId  UNIQUE

I want to fetch following type of data using single query.

items_info._id   |  items_info.Question  |  count(poll_report.answerId) where poll_report.answerId  == 1 |  count(poll_report.answerId) where poll_report.answerId == 2

Can you please help me ?

Answer 1

You probably want something like like this:

select items_info._id , items_info.Question , sum(poll_report.answerId =1) , sum(poll_report.answerId =2) from items_info,poll_report where items_info._id=poll_report.questionId group by items_info._id;

Anyway, the key thing is that you can do this:

sum(poll_report.answerId = 1)