組織図を表示するのが難しいT-SQL（階層/再帰）

編集 OP のテーブルに基づく:

OP のテーブル定義の列を使用した例を次に示します。サンプル データは次のとおりです。

              1-Jerome
                |
              2-Joe
            /       \
     3-Paul          6-David
    /      \            /    \
 4-Jack  5-Daniel   7-Ian    8-Helen


--I only included the needed columns from the OP's table here
DECLARE @Contacts table (id varchar(36), first_name varchar(100), reports_to_id varchar(36))
INSERT @Contacts VALUES ('1','Jerome', NULL )
INSERT @Contacts VALUES ('2','Joe'   ,'1')
INSERT @Contacts VALUES ('3','Paul'  ,'2')
INSERT @Contacts VALUES ('4','Jack'  ,'3')
INSERT @Contacts VALUES ('5','Daniel','3')
INSERT @Contacts VALUES ('6','David' ,'2')
INSERT @Contacts VALUES ('7','Ian'   ,'6')
INSERT @Contacts VALUES ('8','Helen' ,'6')

DECLARE @Root_id  char(4)

--get complete tree---------------------------------------------------
SET @Root_id=null
PRINT '@Root_id='+COALESCE(''''[email protected]_id+'''','null')
;WITH StaffTree AS
(
    SELECT 
        c.id, c.first_name, c.reports_to_id, c.reports_to_id as Manager_id, cc.first_name AS Manager_first_name, 1 AS LevelOf
        FROM @Contacts                  c
            LEFT OUTER JOIN @Contacts  cc ON c.reports_to_id=cc.id
        WHERE [email protected]_id OR (@Root_id IS NULL AND c.reports_to_id IS NULL)
    UNION ALL
        SELECT 
            s.id, s.first_name, s.reports_to_id, t.id, t.first_name, t.LevelOf+1
        FROM StaffTree            t
            INNER JOIN @Contacts  s ON t.id=s.reports_to_id
    WHERE [email protected]_id OR @Root_id IS NULL OR t.LevelOf>1
)
SELECT * FROM StaffTree


--get all below 2---------------------------------------------------
SET @Root_id=2
PRINT '@Root_id='+COALESCE(''''[email protected]_id+'''','null')
;WITH StaffTree AS
(
    SELECT 
        c.id, c.first_name, c.reports_to_id, c.reports_to_id as Manager_id, cc.first_name AS Manager_first_name, 1 AS LevelOf
        FROM @Contacts                  c
            LEFT OUTER JOIN @Contacts  cc ON c.reports_to_id=cc.id
        WHERE [email protected]_id OR (@Root_id IS NULL AND c.reports_to_id IS NULL)
    UNION ALL
        SELECT 
            s.id, s.first_name, s.reports_to_id, t.id, t.first_name, t.LevelOf+1
        FROM StaffTree            t
            INNER JOIN @Contacts  s ON t.id=s.reports_to_id
    WHERE [email protected]_id OR @Root_id IS NULL OR t.LevelOf>1
)
SELECT * FROM StaffTree

--get all below 6---------------------------------------------------
SET @Root_id=6
PRINT '@Root_id='+COALESCE(''''[email protected]_id+'''','null')
;WITH StaffTree AS
(
    SELECT 
        c.id, c.first_name, c.reports_to_id, c.reports_to_id as Manager_id, cc.first_name AS Manager_first_name, 1 AS LevelOf
        FROM @Contacts                  c
            LEFT OUTER JOIN @Contacts  cc ON c.reports_to_id=cc.id
        WHERE [email protected]_id OR (@Root_id IS NULL AND c.reports_to_id IS NULL)
    UNION ALL
        SELECT 
            s.id, s.first_name, s.reports_to_id, t.id, t.first_name, t.LevelOf+1
        FROM StaffTree            t
            INNER JOIN @Contacts  s ON t.id=s.reports_to_id
    WHERE [email protected]_id OR @Root_id IS NULL OR t.LevelOf>1
)
SELECT * FROM StaffTree

出力:

@Root_id=null
id     first_name reports_to_id Manager_id Manager_first_name LevelOf
------ ---------- ------------- ---------- ------------------ -----------
1      Jerome     NULL          NULL       NULL               1
2      Joe        1             1          Jerome             2
3      Paul       2             2          Joe                3
6      David      2             2          Joe                3
7      Ian        6             6          David              4
8      Helen      6             6          David              4
4      Jack       3             3          Paul               4
5      Daniel     3             3          Paul               4

(8 row(s) affected)

@Root_id='2   '
id     first_name reports_to_id Manager_id Manager_first_name LevelOf
------ ---------- ------------- ---------- ------------------ -----------
2      Joe        1             1          Jerome             1
3      Paul       2             2          Joe                2
6      David      2             2          Joe                2
7      Ian        6             6          David              3
8      Helen      6             6          David              3
4      Jack       3             3          Paul               3
5      Daniel     3             3          Paul               3

(7 row(s) affected)

@Root_id='6   '
id     first_name reports_to_id Manager_id Manager_first_name LevelOf
------ ---------- ------------- ---------- ------------------ -----------
6      David      2             2          Joe                1
7      Ian        6             6          David              2
8      Helen      6             6          David              2

(3 row(s) affected)