Question

我在mysql中有一个连接查询

SELECT c.*, r.*
FROM court c
LEFT JOIN reservations r
      ON c.`id` = r.`court_id`
     AND `start_time` < '2016-01-20 11:30:00'
     AND `end_time`   > '2016-01-20 11:00:00'
WHERE  `start_time` IS NULL;

供参考：

reservations.rb 
belongs_to court
fields: start_time,end_time, court_id

courts.rb
has_many reservations
fields: id, name

我试图将其转换为rails，但似乎无法做到。我试过Courts.join(:reservations).on("start_time<'2016-01-20 11:00:00'") 但这不起作用

Answer 1

转换后的版本将是：

Courts.joins('LEFT JOIN reservations ON courts.id = reservations.id')
      .where('reservations.start_time < ? AND reservations.end_time > ?', '2016-01-20 11:30:00', '2016-01-20 11:00:00')
      .where(courts: {start_time: nil})

请注意，joins默认为INNER JOIN，因此我们需要明确指出LEFT JOIN

mysql连接查询到Rails上的ruby

1 个答案: