获取行计数主键表的主键

Question

正如在PK和FK关系如常。

我有两个表一个是让说items_info和第二是poll_report

items_info结构如下

_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 

我想取以下类型的数据使用单个查询。

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

你能帮我吗？

Answer 1

你可能想是这样的：

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; 

不管怎么说，事情的关键是，你可以这样做：

sum(poll_report.answerId = 1)