查询合并3张表 [英] Query combining 3 tables

问题描述

我坚持我的学校项目.我们有3张桌子:

I'm stuck with my school project. We have 3 tables:

filteredtweets(Place, SoortOV, Comment, Time, Date), 
rooster(Lesid, Timestart, Timeend), 
student(studentid, woonplaats, vervoersmiddel)

我们想要一个带有此select语句的列表，但是我想这是错误的:

We want a list with this select statement, but I guess something is wrong:

SELECT student.studentid, student.woonplaats, rooster.Lesid, 
filteredtweets.SoortOV, filteredtweets.Date, filteredtweets.Comment

，我们需要基于2个WHERE子句得出结果:

and we need to have the results based on 2 WHERE clauses:

WHERE filteredtweets.Place = student.woonplaats
WHERE filteredtweets.Time [is 30 minutes in range of] rooster.Timestart

这是我们在PostgreSQL中数据库的屏幕截图.

推荐答案

您可以使用此

SELECT
  s.studentid,
  s.woonplaats,
  s.Lesid,
  f.SoortOV,
  f.Date,
  f.Comment 
 FROM
  filteredtweets f 
  INNER JOIN
      rooster r 
       ON f.Time >= r.Timestart::TIMESTAMP + (30 || ' minutes')::interval 
       OR f.Time <= r.Timestart::TIMESTAMP + (30 || ' minutes')::interval 
 INNER JOIN
     student s 
       ON f.Place = s.woonplaats

这篇关于查询合并3张表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！