SQL Stored procedure Inserts instead of update - sql-server

Question

I have a stored procedure that checks if a record exist and if true then should update else it should insert. But for some weird reason the update does not work and it inserts a record. As a result I have now accumulated duplicate records in the table. How do I ensure that the update works separately from the insert.
CREATE PROCEDURE [dbo].[proc_CustomerAnalysis_Insert]
(
#CustomerID INT,
#UserID INT,
#ProcessCompleted BIT,
#DeliveryDate DATETIME,
#HasOpsNote BIT,
#OpsNote VARCHAR(500),
#isManual BIT,
#FinalStageID INT,
#EffectiveDate DATE,
#Outcome VARCHAR(50),
#ExculdeFromReview BIT
)
AS
BEGIN
DECLARE #TempCustomerAnalysis TABLE
(
CustomerID INT ,
IncreaseDate DATETIME,
Ref VARCHAR(50),
RateIncreaseID INT,
rn INT
)
IF EXISTS(SELECT CustomerID FROM DUmmy9 WHERE DUmmy9.CustomerID = #CustomerID)
BEGIN
WITH UpdateData AS
(
SELECT DISTINCT *
FROM (
SELECT
c.CustomerID CustomerID,
ri.RateIncreasePeriod IncreaseDate,
CONCAT(c.FWRepCode, '\', c.AccountCode) Ref,
ri.RateIncreaseID RateIncreaseID,
u.Name,
row_number() OVER(PARTITION BY c.Name ORDER BY ri.RateIncreasePeriod DESC) AS rn
FROM customers c
left outer join DUmmy1 rc on rc.RateClassID = c.RateClassID
left outer join DUmmy2 css on css.CustomerStatusID = c.CustomerStatusID
left outer join DUmmy3 ri on ri.RateCycleID = rc.RateCycleID
left outer join DUmmy4 fwrm ON fwrm.FWCode = c.FWRepCode
left outer join DUmmy5 rcs ON rcs.RepCodeID = fwrm.RepCodeID
left outer join DUmmy6 u ON u.UserID = rcs.UserID
left outer join DUmmy7 vw on vw.CustomerID = c.CustomerID
WHERE c.CustomerStatusID = 3 AND u.UserID = #UserID AND c.CustomerID = #CustomerID
) t
WHERE t.rn = 1
)
UPDATE DUmmy7
SET IncreaseDate = DUmmy8.IncreaseDate, Ref = DUmmy8.Ref, RateIncreaseID = DUmmy8.RateIncreaseID
FROM UpdateData
WHERE DUmmy8.CustomerID = #CustomerID
END
ELSE
BEGIN
INSERT INTO #TempCustomerAnalysis(CustomerID, IncreaseDate, Ref, RateIncreaseID, rn)
SELECT DISTINCT *
FROM (
SELECT
c.CustomerID CustomerID,
ri.RateIncreasePeriod IncreaseDate,
CONCAT(c.FWRepCode, '\', c.AccountCode) Ref,
ri.RateIncreaseID RateIncreaseID,
row_number() OVER(PARTITION BY c.Name ORDER BY ri.RateIncreasePeriod DESC) AS rn
FROM customers c
left outer join DUmmy1 rc on rc.RateClassID = c.RateClassID
left outer join DUmmy2 css on css.CustomerStatusID = c.CustomerStatusID
left outer join DUmmy3 ri on ri.RateCycleID = rc.RateCycleID
left outer join DUmmy4 fwrm ON fwrm.FWCode = c.FWRepCode
left outer join DUmmy5 rcs ON rcs.RepCodeID = fwrm.RepCodeID
left outer join DUmmy6 u ON u.UserID = rcs.UserID
left outer join DUmmy7 vw on vw.CustomerID = c.CustomerID
WHERE c.CustomerStatusID = 3 AND u.UserID = #UserID AND c.CustomerID = #CustomerID
) t
WHERE t.rn = 1
INSERT INTO DUmmy9(CustomerID, IncreaseDate, ProcessCompleted, DeliveryDate, Ref, HasOpsNote, OpsNote, RateIncreaseID, isManual, FinalStageID, EffectiveDate, Outcome, ExcludeFromReview)
SELECT
CustomerID,
IncreaseDate,
#ProcessCompleted,
#DeliveryDate,
Ref,
#HasOpsNote,
#OpsNote,
RateIncreaseID,
#isManual,
#FinalStageID,
#EffectiveDate,
#Outcome,
#ExculdeFromReview
FROM #TempCustomerAnalysis
END
END

Answer 1

From looking at your example. You never set CustomerAnalysis.CustomerID = #CustomerID before you check the IF ELSE, so that value is always NULL/ never exists in the CustomerAnalysis so ALWAYS goes into the ELSE.

Answer 2

DECLARE #CustomerIDExist INT = (SELECT COUNT(CustomerID) FROM CustomerAnalysis WHERE CustomerAnalysis.CustomerID = #CustomerID)
IF (#CustomerIDExist >= 1)
BEGIN