sql - 对数组值进行内部联接的结果是多条记录

Question

我在 Postgres 中有两个表:

events (id, occurrence_dates) # occurrence_dates is array
dates_calendar (date)

当 events.occurrence_dates 由几个相等的值组成时，{"2017-11-08 00:00:00","2017-11-08 00:00:00"} 2个值为例，下面的查询给出了一条记录:

SELECT "events".* 
FROM "events" 
   INNER JOIN dates_calendar dc ON dc.date = ALL(occurrence_dates)

如何获取与events.occurrence_dates长度一样多的记录？

UPD:我正在使用 Ruby on Rails，但在 SQL 上下文中提供了问题

基于@michel.milezzi 回答的 Rails 作用域:

scope :all_events, -> do
  select("events_sb.*").from(<<-SQL.squish)
    dates_calendar dc
    INNER JOIN (SELECT *, UNNEST(occurrence_dates) oc_date FROM events) AS events_sb
    ON (events_sb.oc_date = dc.date)
  SQL
end

Answer 1

您可以使用 UNNEST扩展数组然后使用常规连接:

-- CTE with test data
WITH dates_calendar(date) AS (
    VALUES 
        ('2017-11-08 00:00:00'::TIMESTAMP), 
        ('2017-11-09 00:00:00'), 
        ('2017-11-10 00:00:00')
), events (id, occurrence_dates) AS (
    VALUES
        (1, '{"2017-11-08 00:00:00", "2017-11-08 00:00:00","2017-11-09 00:00:00","2017-11-10 00:00:00"}'::TIMESTAMP[]), 
        (2, '{"2017-11-08 00:00:00","2017-11-09 00:00:00"}'), 
        (3, '{"2017-11-08 00:00:00"}')
), events_sb AS (
    SELECT id, UNNEST(occurrence_dates) oc_date FROM events
)
SELECT 
    events_sb.* 
FROM 
    dates_calendar dc JOIN events_sb ON (events_sb.oc_date = dc.date) ORDER BY id;

--CTE
WITH events_sb AS (
    SELECT id, UNNEST(occurrence_dates) oc_date FROM events
)
SELECT 
    events_sb.* 
FROM 
    dates_calendar dc JOIN events_sb ON (events_sb.oc_date = dc.date) ORDER BY id;    

--SUBQUERY
SELECT 
    events_sb.* 
FROM 
    dates_calendar dc JOIN (SELECT id, UNNEST(occurrence_dates) oc_date FROM events) AS events_sb ON (events_sb.oc_date = dc.date) ORDER BY id;

要在 Rails 中调用它，您必须执行普通的 sql，这样解释 here和 here .