mysql - MySQL-两次连接同一表

我有一张叫“预订”的桌子

> id     status
  1      P
  2      P

还有一个叫做“通话”

id    calldate    type   booking
1     01/01/2012  DEL    1
2     01/02/2012  COL    1
3     01/03/2012  DEL    2
4     31/12/2019  COL    999

我想在“预订”一次列出每个记录，将来自“通话”的关联记录显示为这样的另一列：

bookingId    deliverydate  collectiondate
1            01/01/2012    01/02/2012
2            01/03/2012    null

我试过了：

select `b`.`bookingid` AS `bookingid`,
       `del`.`calldate` AS `Delivery`,
       `col`.`calldate` AS `Collection`
from `booking` `b`
left join `call` `del` on `b`.`bookingid` = `del`.`booking`
left join `call` `col` on `b`.`bookingid` = `col`.`booking`
where ((`del`.`type` = 'DEL') OR (`col`.`type` = 'COL') and (`b`.`status` = 'P'));

但我得到Bookingid 1列出了3次。有人可以修复我的联接吗？

最佳答案

我认为您想将类型移动到联接条件中：

select `b`.`bookingid` AS `bookingid`,
   `del`.`calldate` AS `Delivery`,
   `col`.`calldate` AS `Collection`
from `booking` `b`
left join `call` `del` on `b`.`bookingid` = `del`.`booking` AND `del`.`type` = 'DEL'
left join `call` `col` on `b`.`bookingid` = `col`.`booking` AND `col`.`type` = 'COL'
where `b`.`status` = 'P';

关于mysql - MySQL-两次连接同一表，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/13943350/