Question

我有以下2个表格：

CREATE TABLE [Names] 
    (
    [Id] INT PRIMARY KEY,
    [Name] VARCHAR(100)
    )

CREATE TABLE [Relationships]
    (
    [Parent] [int] REFERENCES [Names]([Id]), 
    [Child] [int] REFERENCES [Names]([Id])
    )

Sample Data:

INSERT [NAMES] VALUES (1,'FRANK')
INSERT [NAMES] VALUES (2,'JO')
INSERT [NAMES] VALUES (3,'MARY')
INSERT [NAMES] VALUES (4,'PETER')
INSERT [NAMES] VALUES (5,'MAY')

INSERT [RELATIONSHIPS] VALUES (1,2)
INSERT [RELATIONSHIPS] VALUES (2,3)
INSERT [RELATIONSHIPS] VALUES (4,2)
INSERT [RELATIONSHIPS] VALUES (5,4)

如何显示嵌套（树）名称列表，包括[Id]，[Name]和[Level]，其中[Level]表示从顶部开始的嵌套级别（Root：Level = 0; Root的第一个子级：等级= 1;等等......）？例如，结果应显示：

Level     Relationship
-----     ------------
2         FRANK <- JO
3         FRANK <- JO <- MARY
2         PETER <- JO
3         MAY <- PETER <- JO

Answer 1

您可以考虑切换到Hierarchical Data。 TSQL支持它很好，你不需要重新发明轮子＆＃39;。从长远来看，这将使您的查询更容易。

Go here for a nice tutorial on the subject.

Answer 2

试试这个：

with Relatives as
(
    select n.Id, cast(n.Name as varchar(max)) Relationship, 0 [Level]
    from Names n
    where not exists
    (
        select *
        from Relationships r
        where n.Id = r.Child
    )

    union all

    select n.Id, p.Relationship + ' <- ' + n.Name Relationship, p.[Level] + 1 [Level]
    from Names n
    join Relationships r
        on n.Id = r.Child
    join Relatives p
        on r.Parent = p.Id
)

select Relationship, [Level]
from Relatives

T-SQL递归查询显示嵌套的Tree结构

2 个答案: