如何從Mysql中的分層數據獲取位置名稱？

Question

我有表Location這樣的：

ID, PID, Location 
1 NuLL Country 
2 1  City 
3 2  County 
4 3  District 
5 4  Social 

如何使MySQL中的觀點，即返回此：

ID, Location, Full Location 
1  Country  Country 
2  City  City-Country 
3  County  County-City-Country 
4  District District-County-City-Country 
5  Social  Social-District-County-City-Country 

Answer 1

您可以加入或變量做到這一點。但是，視圖中不允許使用變量。所以，這樣的事情：

select concat_ws('-', l.location, l1.location, l2.location, l3.location, l4.location) 
from location l left join 
    location l1 
    on l1.pid = l.id left join 
    location l2 
    on l2.pid = l1.id left join 
    location l3 
    on l3.pid = l2.id left join 
    location l4 
    on l4.pid = l3.id ;