mysql - 如何从 Mysql 中的分层数据中获取位置名称？

Question

我有这样的表 Location:

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

如何在 MySQL 中创建一个返回此 View 的 View :

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

您可以使用连接或变量来做到这一点。但是， View 中不允许使用变量。所以，像这样:

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 ;