Question

我正在学习SQL，我需要进行查询以提供所有事件，但是我有特殊性。 FK id_festival可以为null，表事件中的nb_tickets_sold列也可以为null。

我尝试进行以下查询，但没有结果

CREATE VIEW project.showEvents AS 
SELECT ev.id_event AS "ID",
ev.event_name AS "Name",
ev.price AS "Price",
fe.festival_name AS "Festival",
ev.event_date AS "Date",
ch.concert_hall_name AS "Hall"
FROM project.concerts co,  project.concert_halls ch,
project.events ev LEFT OUTER JOIN project.festivals fe ON ev.id_festival = fe.id_festival
WHERE ev.id_event = co.id_event
AND ev.id_concert_hall = ch.id_concert_hall
ORDER BY ev.event_date;

Answer 1

不要将隐含和显式加入

  CREATE VIEW project.showEvents AS 
  SELECT ev.id_event AS "ID",
  ev.event_name AS "Name",
  ev.price AS "Price",
  fe.festival_name AS "Festival",
  ev.event_date AS "Date",
  ch.concert_hall_name AS "Hall"
  FROM project.concerts co
  INNER JOIN   project.concert_halls ch ON ev.id_concert_hall = ch.id_concert_hall
  INNER project.events ev  ON ev.id_event = co.id_event
  LEFT OUTER JOIN project.festivals fe ON ev.id_festival = fe.id_festival
  ORDER BY ev.event_date;

我的左外部联接在PostgreSQL中不起作用

1 个答案: