如何从Mysql中的分层数据获取位置名称？

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中创建一个返回此视图的视图：

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执行此操作。但是，视图中不允许使用变量。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 ;