在单个表的多个不同字段上选择不同的条件

Question

你好，我想要以下内容（不使用子查询）：

select planName where period=1 as 1stPlan
select planName where period=2 as 2ndPlan
select planName where period=3 as 3ndPlan
...
FROM plan inner join project ON Project.Id=Plan.ProjectId

谢谢

Answer 1

select
  plan1.planName,
  plan2.planName,
  plan3.planName 
FROM project 
  left join plan plan1 ON Project.Id=Plan1.ProjectId and Plan1.period=1 
  left join plan plan2 ON Project.Id=Plan2.ProjectId and Plan2.period=2 
  left join plan plan3 ON Project.Id=Plan3.ProjectId and Plan3.period=3