左联接两个不同的值

Question

tab_city

 id_city   city
  1       Paris
  2       Texas
  3       Toquio

tab_control

id_control origin  destination
 1             1           3

对于以前的表格，我需要从tab_control获取数据，并从tab_city获取相应的城市。

如果仅是起源，则非常简单：

SELECT origin.tco, city.tci
FROM tab_control tco
LEFT JOIN tab_city tci ON tco.origin = tci.id_city

返回

origin = 1
city = Paris

但是，我需要得到

origin = 1
city = Paris
destination = 3
city_destination?? = Toquio

Answer 1

您需要另一个JOIN作为目的地

SELECT tco.origin, tci.city, tco.destination, d.city
FROM tab_control tco
LEFT JOIN tab_city tci ON tco.origin = tci.id_city
LEFT JOIN tab_city d ON tco.destination = d.id_city