Variable is declared but error messages says not - sql

Question

In the stored procedure shown below, I get this error, but I am declaring the #Remarks, so I cannot see what is the issue:
Msg 137, Level 15, State 2, Procedure sp_Insert_EMR_PATIENT_CHECK_TRACKING, Line 53
Must declare the scalar variable "#REMARKS".
Code:
create PROCEDURE [dbo].[sp_Insert_EMR_PATIENT_CHECK_TRACKING]
#HOUR int,
#TIME int,
#MRN nchar(10),
#NURSING_UNIT varchar(12),
#CHECK_DATE datetime,
#MONITOR_CODE nchar(10),
#Remarks nvarchar(500),
#Pain_Level int
AS
BEGIN
SET NOCOUNT ON;
If #Remarks = 'undefined'
BEGIN
SET #Remarks = null
END
IF NOT EXISTS (SELECT *
FROM [OGEN].[EMR_PATIENT_CHECK_TRACKING]
WHERE CHECK_DATE = #CHECK_DATE
AND MRN = #MRN
AND NURSING_UNIT = #NURSING_UNIT
AND HOUR = #HOUR
AND TIME = #TIME
AND MONITOR_CODE = #MONITOR_CODE)
BEGIN
INSERT INTO [OGEN].[EMR_PATIENT_CHECK_TRACKING] ([CHECK_DATE], [MRN], [NURSING_UNIT], [HOUR], [TIME], [MONITOR_CODE], [Pain_Level])
VALUES (#CHECK_DATE, #MRN, #NURSING_UNIT, #HOUR, #TIME, #MONITOR_CODE, #Pain_Level)
IF NOT EXISTS (SELECT *
FROM [OGEN].[EMR_PATIENT_CHECK_TRACKING_REMARK]
WHERE CHECK_DATE = #CHECK_DATE
AND MRN = #MRN
AND NURSING_UNIT = #NURSING_UNIT
AND HOUR = #HOUR
AND MONITOR_CODE = #MONITOR_CODE)
BEGIN
INSERT INTO [OGEN].[EMR_PATIENT_CHECK_TRACKING_REMARK] ([CHECK_DATE], [MRN], [NURSING_UNIT], [HOUR], [MONITOR_CODE], [REMARKS])
VALUES (#CHECK_DATE, #MRN, #NURSING_UNIT, #HOUR, #MONITOR_CODE, ISNULL(#REMARKS,''))
END
ELSE
BEGIN
UPDATE [OGEN].[EMR_PATIENT_CHECK_TRACKING_REMARK]
SET REMARKS = ISNULL(#Remarks,REMARKS)
WHERE CHECK_DATE = #CHECK_DATE
AND [MRN] = #MRN
AND [NURSING_UNIT] = #NURSING_UNIT
AND [HOUR] = #HOUR
AND [MONITOR_CODE] = #MONITOR_CODE
END
END
ELSE
BEGIN
UPDATE [OGEN].[EMR_PATIENT_CHECK_TRACKING]
SET [Pain_Level]=#Pain_Level
WHERE CHECK_DATE = #CHECK_DATE
AND MRN = #MRN
AND NURSING_UNIT = #NURSING_UNIT
AND HOUR = #HOUR
AND TIME = #TIME
AND MONITOR_CODE = #MONITOR_CODE
UPDATE [OGEN].[EMR_PATIENT_CHECK_TRACKING_REMARK]
SET REMARKS = Isnull(#Remarks,REMARKS)
WHERE CHECK_DATE = #CHECK_DATE
AND [MRN] = #MRN
AND [NURSING_UNIT] = #NURSING_UNIT
AND [HOUR] = #HOUR
AND [MONITOR_CODE] = #MONITOR_CODE
END
END

Answer 1

The parameter #Remarks is declared using camel case and later in your stored procedure you reference it as #REMARKS - it could be that you are using a case-sensitive collation and this will result in the error you are seeing.
If your database collation contains "_CI" (e.g. Latin1_General_CI_AS) then it is case-insensitive, if it contains "_CS" it is a case-sensitive collation.

Answer 2

Based on the error information, your server is set to be case-sensitive. This can be confirmed via,
SELECT CONVERT (varchar, SERVERPROPERTY('collation'));
Running the above statement on my case-sensitive server returns, SQL_Latin1_General_CP1_CS_AS.
To bypass that error, you must rename #REMARKS to #Remarks which you had defined or append a COLLATE statement to change the sensitivity to be case-insensitive. On my server, this would be SQL_Latin1_General_CP1_CI_AS.
The better choice would be to remain consistent with your variable naming convention.
On the same case-sensitive server,
DECLARE #value VARCHAR(10) = 'hello'
SELECT #VALUE <<< ERROR.
SELECT #value COLLATE SQL_Latin1_General_CP1_CI_AS <<< returns, 'hello'