SQL Query Peers and above - sql

Question

There are recursive queries available to find all children or parents in a hierarchy (for example in an employee-manager hierarchy) but I couldn't find any example of peers and above/parents
EmpID FName LName MgrID
11 Sally Smith NULL
1 Alex Adams 11
2 Barry Brown 11
3 Lee Osaka 11
4 David Kennson 11
5 Eric Bender 11
7 David Lonning 11
6 Lisa Kendall 4
8 John Marshbank 4
12 Barbara ONeill 4
13 Phil Wilconkinski 4
9 James Newton 3
10 Terry OHaire 3
So if I want peer-above of EmpID=6 then it should return
EmpID FName LName MgrID
11 Sally Smith NULL grandparent/peer
1 Alex Adams 11 parent-peer
2 Barry Brown 11 parent-peer
3 Lee Osaka 11 parent-peer
4 David Kennson 11 (parent of id=6)
5 Eric Bender 11 parent-peer
7 David Lonning 11 parent-peer
6 Lisa Kendall 4 (id=6)
8 John Marshbank 4 peer
12 Barbara ONeill 4 peer
13 Phil Wilconkinski 4 peer
Any help will be very appreciated

Answer 1

With the way your table is currently structured, one way of achieving this is to include a path in your recursive CTE, then parse the path to figure out whether someone belongs to that path in the hierarchy.
For example,
DECLARE #Table TABLE
(
EmpID INT NOT NULL,
FName VARCHAR(20) NOT NULL,
LName VARCHAR(20) NOT NULL,
MgrID INT
);
INSERT #Table (EmpID, FName, LName, MgrID)
VALUES
(11, 'Sally', 'Smith', NULL),
(1, 'Alex', 'Adams', 11),
(2, 'Barry', 'Brown', 11),
(3, 'Lee', 'Osaka', 11),
(4, 'David', 'Kennson', 11),
(5, 'Eric', 'Bender', 11),
(7, 'David', 'Lonning', 11),
(6, 'Lisa', 'Kendall', 4),
(8, 'John', 'Marshbank', 4),
(12, 'Barbara', 'ONeill', 4),
(13, 'Phil', 'Wilconkinski', 4),
(9, 'James', 'Newton', 3),
(10, 'Terry', 'OHaire', 3);
WITH CTE AS
(
SELECT EmpID,
FName,
LName,
MgrID,
Tree = CAST(EmpID AS VARCHAR(255)),
Lvl = 1
FROM #Table
WHERE MgrID IS NULL
UNION ALL
SELECT T.EmpID,
T.FName,
T.LName,
T.MgrID,
CAST(CTE.Tree + '-' + CAST(T.EmpID AS VARCHAR(255)) AS VARCHAR(255)), -- Your paths will look like '11-4-6'.
CTE.Lvl + 1
FROM CTE
JOIN #Table T ON T.MgrID = CTE.EmpID
)
SELECT EmpID,
FName,
LName,
MgrID,
Lvl,
Direct = CASE MIN(CASE WHEN EmpID = Item THEN 1 ELSE 2 END) WHEN 1 THEN 'Direct' ELSE 'Peer' END
FROM CTE
JOIN
(
SELECT Item
FROM CTE
CROSS APPLY dbo.[DelimitedSplit8K](Tree, '-') D
WHERE CTE.EmpID = 6
) D ON D.Item = CTE.EmpID
OR D.Item = CTE.MgrID
GROUP BY EmpID, FName, LName, MgrID, Lvl;
This uses a split function to break up the path and only display people in that path. The split function can be found here and looks like this:
CREATE FUNCTION [dbo].[DelimitedSplit8K]
--===== Define I/O parameters
(#pString VARCHAR(8000), #pDelimiter CHAR(1))
--WARNING!!! DO NOT USE MAX DATA-TYPES HERE! IT WILL KILL PERFORMANCE!
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
--===== "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
-- enough to cover VARCHAR(8000)
WITH E1(N) AS (
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
), --10E+1 or 10 rows
E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
-- for both a performance gain and prevention of accidental "overruns"
SELECT TOP (ISNULL(DATALENGTH(#pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
SELECT 1 UNION ALL
SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(#pString,t.N,1) = #pDelimiter
),
cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
SELECT s.N1,
ISNULL(NULLIF(CHARINDEX(#pDelimiter,#pString,s.N1),0)-s.N1,8000)
FROM cteStart s
)
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),
Item = SUBSTRING(#pString, l.N1, l.L1)
FROM cteLen l
;