Can we reduce multiple joins to same table - sql

Question

I have following stored procedure:
ALTER PROCEDURE GetNotes
#ResidentId INT,
#Type INT = 0
AS
BEGIN
SET NOCOUNT ON;
DECLARE #myTab TABLE
(
Residentid int NOT NULL,
Description nvarchar(max) NULL,
CreatedOn DATETIME2(7) NULL,
CreatedBy NVARCHAR(MAX) NULL,
NoteTypeId int NULL
)
INSERT INTO #myTab (Residentid, Description, CreatedOn, CreatedBy, NoteTypeId)
SELECT
R.Id,
v.[Description],
v.[Date],
v.[CreatedBy],
v.Col
FROM
Resident R
LEFT JOIN
Invoice AS I ON I.ResidentId = R.Id
LEFT JOIN
ResidentCourse AS RC ON RC.ResidentId = R.Id
--- LEFT JOIN ON USERS FOR Getting CreatedBy Column ---
LEFT JOIN
USERS AS Ui ON I.CreatedBy = Ui.Id
LEFT JOIN
USERS AS Urc ON rc.CreatedBy = Urc.Id
LEFT JOIN
Resident AS UR ON R.CreatedBy = UR.Id
CROSS APPLY
(VALUES (1, R.CreatedDate, R.Notes, UR.FirstName + ' '+ UR.LastName),
(3, I.Date, I.Description, UI.FirstName + ' '+ UI.LastName),
(4, RC.Date, RC.Notes, URC.FirstName + ' '+ URC.LastName),
) v (Col, [Date], [Description], [CreatedBy])
WHERE
R.Id = #ResidentId
SELECT DISTINCT
Residentid,
Description,
CreatedBy,
CreatedOn,
NoteTypeId
FROM
#myTab
WHERE
Description IS NOT NULL
AND CreatedOn IS NOT NULL
AND (#Type = 0 OR NoteTypeId = #Type)
ORDER BY
CreatedOn DESC
END
Result
Id Description CreatedBy CreatedOn NoteTypeId
-------- ---------- ------------------------------------------
1 ASD ASD John Doe 2020-01-02 1
4 ASD DSS Terry kal 2020-01-02 3
I have a Note column in every table and a CreatedBy column also so in above stored procedure I am performing a LEFT JOIN on the Users table for getting the name of that user. Considering I have 8 different tables with Note / Description columns, right now I have 8 LEFT JOIN against the Users table to get data.
Is there an optimal solution?
Any help would be appreciated.

Answer 1

Instead of joining I, R and RC to Users, you could put each CreatedBy in #MyTab and join in the second query.
DECLARE #myTab TABLE
(
Residentid int NOT NULL,
Description nvarchar(max) NULL,
CreatedOn DATETIME2(7) NULL,
CreatedBy int NULL,
NoteTypeId int NULL
)
INSERT INTO #myTab (Residentid, Description, CreatedOn, CreatedBy, NoteTypeId)
SELECT
R.Id,
v.[Description],
v.[Date],
v.[CreatedBy],
v.Col
FROM
Resident R
LEFT JOIN
Invoice AS I ON I.ResidentId = R.Id
LEFT JOIN
ResidentCourse AS RC ON RC.ResidentId = R.Id
CROSS APPLY
(VALUES (1, R.CreatedDate, R.Notes, UR.CreatedBy ),
(3, I.Date, I.Description, UI.CreatedBy ),
(4, RC.Date, RC.Notes, URC.CreatedBy ),
) v (Col, [Date], [Description], [CreatedBy])
WHERE
R.Id = #ResidentId
SELECT DISTINCT
T.Residentid,
T.Description,
U.FirstName + ' ' + U.LastName,
T.CreatedOn,
T.NoteTypeId
FROM
#myTab AS T
LEFT JOIN
USERS AS U ON T.CreatedBy = U.Id
WHERE
Description IS NOT NULL
AND CreatedOn IS NOT NULL
AND (#Type = 0 OR NoteTypeId = #Type)
ORDER BY
CreatedOn DESC

Answer 2

Give this a whirl:
WITH some_cte AS (
SELECT 'Resident' AS DataSource
, Id AS ResidentId
, Notes AS Description
, CreatedDate AS CreatedOn
, CreatedBy AS CreatedByUserId
FROM Resident
WHERE Notes IS NOT NULL
AND CreatedDate IS NOT NULL
AND Id = #ResidentId
AND #Type IN (0, 1)
UNION ALL
SELECT 'Invoice' AS DataSource
, ResidentId
, Description
, [Date] AS CreatedOn
, CreatedBy AS CreatedByUserId
FROM Description IS NOT NULL
AND [Date] IS NOT NULL
AND ResidentId = #ResidentId
AND #Type IN (0, 3)
UNION ALL
SELECT 'ResidentCourse' AS DataSource
, ResidentId
, Notes AS Description
, [Date] AS CreatedOn
, CreatedBy AS CreatedByUserId
FROM ResidentCourse
WHERE Notes IS NOT NULL
AND [Date] IS NOT NULL
AND ResidentId = #ResidentId
AND #Type IN (0, 4)
)
SELECT some_cte.DataSource
, some_cte.ResidentId
, some_cte.CreatedOn
, some_cte.Description
, some_cte.CreatedByUserId
, Users.FirstName + ' ' + Users.LastName AS CreatedBy
FROM some_cte
INNER
JOIN Users
ON Users.Id = some_cte.CreatedByUserId
ORDER
BY some_cte.CreatedOn DESC
;
The join to Users is now only performed once, but might be sub-optimal. Should it be a problem you can inline the join to Users on each individual query.