Question

我有两个像这样定义的表。表位置用于存储地址

locations
---------
id
addr
city
zip
name

另一个表引用每个条目的位置表中的两个位置地址存储是

packages
---------
id
client_id
pick_id  <-- this id is for the location address for pick
drop_id  <-- this id is for the location address for drop

我想要回归

location.name, location.addr, location.city, location.id for pick
location.name, location.addr, location.city, location.id for drop

对于给定的client_id

我目前有这个sql

Select
  packages.status,
  locations.name,
  locations.address,
  locations.zip,
  locations.city,
  locations.id
From
  packages Inner Join
  locations On packages.drop_id = locations.id And packages.client_id = 5

但是我得到了空行结果。任何人都可以指出我的错误吗？

Answer 1

不应该是：

...
ON packages.drop_id = locations.id
WHERE packages.client_id = 5

？由于JOIN未使用packages.client_id。

Answer 2

您似乎只是针对位置表格，而是针对每个放置和选择位置。

要做到这两点，请使用以下内容： -

Select
  packages.status,
  PickLocation.name,
  PickLocation.address,
  PickLocation.zip,
  PickLocation.city,
  PickLocation.id,
  DropLocation.name,
  DropLocation.address,
  DropLocation.zip,
  DropLocation.city,
  DropLocation.id
From packages 
INNER JOIN locations AS PickLocation ON packages.pick_id = PickLocation.id
INNER JOIN locations AS DropLocation ON packages.drop_id = DropLocation.id
WHERE packages.client_id = 5

如果没有返回任何记录，则表明客户端ID 5没有包，或者drop或pick up位置不在位置表上。如果后者尝试使用LEFT OUTER JOIN而不是INNER JOINs

从表中进行多项选择

2 个答案: