SQL查询层级号

Question

这是数据：

CREATE TABLE dbo.Correspondents
(
    ID smallint NOT NULL,
    ParentID smallint NULL,
    Name nvarchar(30)  NOT NULL,
    OrderNumber int NOT NULL
);

INSERT INTO dbo.Correspondents VALUES 
 (1, null, 'A', 1),
 (2, 1, 'B', 2),
 (3, 1, 'C', 3),
 (4, 2, 'D', 1);

我想要的结果：

ID|Name|HierarchicalNumber
1 |   A|   1
2 |   B|   1.2
3 |   C|   1.3
4 |   D|   1.2.1

线索是每个条目都有自己的订单号，但查询应该 return 包含所有父编号的层次编号作为子序列，由末尾带有自己编号的点分隔。主要功能要求能够为任何条目提供层次编号，因此查询应该能够接收条目的 ID 并 return 它的层次编号。数据库管理系统是 MSSQL 2017。提前致谢！

Answer 1

你想要递归 CTE

with h as (
  select *, cast(OrderNumber as varchar(max)) hid
  from dbo.Correspondents
  where ParentID is null
  
  union all
  select c.*, h.hid + '.' + cast(c.OrderNumber as varchar(10)) 
  from dbo.Correspondents c
  join h on h.id= c.ParentID
  )
select *
from h
order by hid;

它也可以重构为 TVF

create function gethid(@id int) returns table
as return
    with h as (
      select *, cast(OrderNumber as varchar(max)) hid
      from dbo.Correspondents
      where ParentID is null
      
      union all
      select c.*, h.hid + '.' + cast(c.OrderNumber as varchar(10)) 
      from dbo.Correspondents c
      join h on h.id= c.ParentID
           -- stop when @id is found
           and h.id != @id
      )
    select *
    from h
    where id = @id;

db<>fiddle

Answer 2

看起来像一个简单的递归查询，在其中构建层次结构字符串，从您正在获取的新行的父行中已有的内容开始 - 作为连续的字符串连接。

像下面一样 - 或者您正在寻找其他东西？

WITH rec AS (
  SELECT
    id  
  , name
  , CAST(id AS VARCHAR(16)) AS hierarchicalnumber
  FROM correspondents
  WHERE parentid IS NULL
  UNION ALL 
  SELECT
    correspondents.id
  , correspondents.name
  ,   rec.hierarchicalnumber 
    + '.' 
    + CAST(correspondents.id AS VARCHAR(16)) AS hierarchialnumber                                                                                                          
  FROM correspondents JOIN rec ON rec.id = correspondents.parentid
)
SELECT * FROM rec;
-- out  id | name | hierarchicalnumber 
-- out ----+------+--------------------
-- out   1 | A    | 1
-- out   2 | B    | 1.2
-- out   3 | C    | 1.3
-- out   4 | D    | 1.2.4

SQL查询层级号

SQL query for hierarchical number

sql

sql-server

recursive-query