Comparison results between two select statements in a stored procedure - sql-server

Question

I want to start off by saying that I am brand new to Stored Procedures, and am basically teaching myself how to do them. Any suggestions or advice will be greatly appreciated. I would mail you chocolate if I could.
The Gist: My organization's clients take a survey on their initial visit and on each 6th subsequent visits. We need to know if the individual has shown improvement over time. The way we decided to do this is compare the 1st to the most recent. So if they have been to 18 sessions, it would be the 1st and 3rd surveys that are compared (because they would have completed the survey 3 times over 18 sessions).
I have been able to obtain the "first" score and the "recent" score with two complex, multiple layered-nested select statements inside of one stored procedure. The "first" one is a TOP(1) linking on unique id (DOCID) and then ordered by date. The "recent" one is a TOP(1) linking on unique id (DOCID) and then ordered by date descending. This gets me exactly what I need within each statement, but it does not output what I need correctly which is obviously to the ordering in the statements.
The end result will be to create a Crystal Report with it for grant reporting purposes.
Declare
#StartDate Date,
#EndDate Date,
#First_DOCID Int,
#First_Clientkey Int,
#First_Date_Screening Date,
#First_Composite_Score Float,
#First_Depression_Score Float,
#First_Emotional_Score Float,
#First_Relationship_Score Float,
#Recent_DOCID Int,
#Recent_Clientkey Int,
#Recent_Date_Screening Date,
#Recent_Composite_Score Float,
#Recent_Depression_Score Float,
#Recent_Emotional_Score Float,
#Recent_Relationship_Score Float,
#Difference_Composit_Score Float,
#Difference_Depression_Score Float,
#Difference_Emotional_Score Float,
#Difference_Relationship_Score Float
SET #StartDate = '1/1/2016'
SET #EndDate = '6/1/2016'
BEGIN
SELECT #First_DOCID = CB24_1.OP__DOCID, #First_Date_Screening = CB24_1.Date_Screening, #First_Clientkey = CB24_1.ClientKey, #First_Composite_Score = CB24_1.Composite_score, #First_Depression_Score = CB24_1.Depression_Results, #First_Emotional_Score = CB24_1.Emotional_Results, #First_Relationship_Score = CB24_1.Relationships_Results
FROM FD__CNSLG_BASIS24 AS CB24_1
WHERE (CB24_1.OP__DOCID =
(Select TOP(1) CB24_2.OP__DOCID
...
ORDER BY CB24_2.Date_Screening))
ORDER BY ClientKey DESC
END
BEGIN
SELECT #Recent_DOCID = CB24_1.OP__DOCID, #Recent_Date_Screening = CB24_1.Date_Screening, #Recent_Clientkey = CB24_1.ClientKey, #Recent_Composite_Score = CB24_1.Composite_score, #Recent_Depression_Score = CB24_1.Depression_Results, #Recent_Emotional_Score = CB24_1.Emotional_Results, #Recent_Relationship_Score = CB24_1.Relationships_Results
FROM FD__CNSLG_BASIS24 AS CB24_1
WHERE (CB24_1.OP__DOCID =
(Select TOP(1) CB24_2.OP__DOCID
...
ORDER BY CB24_2.Date_Screening DESC))
ORDER BY ClientKey
END
SET #Difference_Composit_Score = (#Recent_Composite_Score - #First_Composite_Score)
SET #Difference_Depression_Score = (#Recent_Depression_Score - #First_Depression_Score)
SET #Difference_Emotional_Score = (#Recent_Emotional_Score - #First_Emotional_Score)
SET #Difference_Relationship_Score = (#Recent_Relationship_Score - #First_Relationship_Score)
SELECT
#First_DOCID AS First_Docid,
#First_Clientkey AS First_Clientkey,
#First_Date_Screening AS First_Date_Screening,
#First_Composite_Score AS First_Composite_Score,
#First_Depression_Score AS First_Depression_Score,
#First_Emotional_Score AS First_Emotional_Score,
#First_Relationship_Score AS First_Relationship_Score,
#Recent_DOCID AS Recent_DOCID,
#Recent_Clientkey AS Recent_Clientkey,
#Recent_Date_Screening AS Recent_Date_Screening,
#Recent_Composite_Score AS Recent_Composite_Score,
#Recent_Depression_Score AS Recent_Depression_Score,
#Recent_Emotional_Score AS Recent_Emotional_Score,
#Recent_Relationship_Score AS Recent_Relationship_Score,
#Difference_Composit_Score AS Difference_Composit_Score,
#Difference_Depression_Score AS Difference_Depression_Score,
#Difference_Emotional_Score AS Difference_Emotional_Score,
#Difference_Relationship_Score AS Difference_Relationship_Score

Answer 1

In SQL you don't want unnecessary declared variables.
Here's a contrived but reproducible example which utilizes common table expressions and window functions that should get you in the right direction. I created the stored procedure from the template with the necessary input parameters (which in real life you'd like to avoid).
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE dbo.Client_Improvement_Results
(#StartDate DATETIME, #EndDate DATETIME)
AS
BEGIN
SET NOCOUNT ON;
-- Insert statements for procedure here
-- You would never do this in real-life but for a simple reproducible example...
DECLARE #Survey TABLE
(
Clientkey INT,
Date_Screening DATE,
Composite_Score FLOAT
)
INSERT INTO #Survey
VALUES
(1, '2014-04-01', 42.1),
(1, '2014-04-10', 46.1),
(1, '2014-04-20', 48.1),
(2, '2014-05-10', 40.1),
(2, '2014-05-20', 30.1),
(2, '2014-05-30', 10.1)
;
--Use Common Table Expression & Window Functions to ID first/recent visit by client
WITH CTE AS (
SELECT
S.Clientkey
,S.Composite_Score
,S.Date_Screening
,First_Date_Screening = MIN(S.Date_Screening) OVER(PARTITION BY S.Clientkey)
,Recent_Date_Screening = MAX(S.Date_Screening) OVER(PARTITION BY S.Clientkey)
FROM #Survey AS S
)
--Self join of CTE with proper filters
--applied allows you to return differences in one row
SELECT
f.Clientkey
,f.First_Date_Screening
,f.Recent_Date_Screening
,Difference_Score = r.Composite_Score - f.Composite_Score
FROM
CTE AS f --first
INNER JOIN CTE AS r --recent
ON f.Clientkey = r.Clientkey
WHERE
f.Date_Screening = f.First_Date_Screening
AND r.Date_Screening = r.Recent_Date_Screening
END
GO

Answer 2

Here is the solution I came up with after everyone amazing advice.
I want to go back and replace the TOP(1) with another new thing I learned at some point:
select pc.*
from (select pc.*, row_number() over (partition by Clientkey, ProgramAdmitKey order by Date_Screening) as seqnum
from FD__CNSLG_BASIS24 PC) pc
where seqnum = 1
I will have to play with the above script a bit first, however. It doesn't like to be inserted into the larger script below.
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
BEGIN
SET NOCOUNT ON;
Declare
#StartDate Date,
#EndDate Date
SET #StartDate = '1/1/2016'
SET #EndDate = '6/1/2016'
WITH CNSL_Clients AS (
SELECT PC_CNT.Clientkey, PC_Cnt.ProgramAdmitKey, PC_Cnt.OP__DOCID
FROM FD__Primary_Client as PC_Cnt
INNER JOIN VW__Cnsl_Session_Count_IndvFamOnly as cnt
ON PC_Cnt.Clientkey = CNT.Clientkey AND PC_Cnt.ProgramAdmitKey = CNT.ProgramAdmitKey
WHERE ((pc_CNT.StartDate between #StartDate AND #EndDate) OR (pc_CNT.StartDate <= #StartDate AND pc_CNT.ENDDate >= #StartDate) OR (pc_CNT.StartDate <= #StartDate AND pc_CNT.ENDDate is null))
AND CNT.SessionCount>=6
),
FIRST_BASIS AS (
SELECT CB24_1.OP__DOCID, CB24_1.Date_Screening, CB24_1.ClientKey, CB24_1.ProgramAdmitKey, CB24_1.Composite_score, CB24_1.Depression_Results,CB24_1.Emotional_Results, CB24_1.Relationships_Results
FROM FD__CNSLG_BASIS24 AS CB24_1
WHERE (CB24_1.OP__DOCID =
(Select TOP(1) CB24_2.OP__DOCID
FROM FD__CNSLG_BASIS24 AS CB24_2
Inner JOIN CNSL_Clients
ON CB24_2.ClientKey = CNSL_Clients.ClientKey AND CB24_2.ProgramAdmitKey = CNSL_Clients.ProgramAdmitKey
WHERE (CB24_1.ClientKey = CB24_2.ClientKey) AND (CB24_1.ProgramAdmitKey = CB24_2.ProgramAdmitKey)
ORDER BY CB24_2.Date_Screening))
),
RECENT_BASIS AS (
SELECT CB24_1.OP__DOCID, CB24_1.Date_Screening, CB24_1.ClientKey, CB24_1.ProgramAdmitKey, CB24_1.Composite_score, CB24_1.Depression_Results,CB24_1.Emotional_Results, CB24_1.Relationships_Results
FROM FD__CNSLG_BASIS24 AS CB24_1
WHERE (CB24_1.OP__DOCID =
(Select TOP(1) CB24_2.OP__DOCID
FROM FD__CNSLG_BASIS24 AS CB24_2
Inner JOIN CNSL_Clients
ON CB24_2.ClientKey = CNSL_Clients.ClientKey AND CB24_2.ProgramAdmitKey = CNSL_Clients.ProgramAdmitKey
WHERE (CB24_1.ClientKey = CB24_2.ClientKey) AND (CB24_1.ProgramAdmitKey = CB24_2.ProgramAdmitKey)
ORDER BY CB24_2.Date_Screening DESC))
)
SELECT F.OP__DOCID AS First_DOCID,R.OP__DOCID as Recent_DOCID,F.ClientKey, F.ProgramAdmitKey, F.Composite_Score AS FComposite_Score, R.Composite_Score as RComposite_Score, Composite_Change = R.Composite_Score - F.Composite_Score, F.Depression_Results AS FDepression_Results, R.Depression_Results AS RDepression_Resluts, Depression_Change = R.Depression_Results - F.Depression_Results, F.Emotional_Results AS FEmotional_Resluts, R.Emotional_Results AS REmotionall_Reslu, Emotional_Change = R.Emotional_Results - F.Emotional_Results, F.Relationships_Results AS FRelationships_Resluts, R.Relationships_Results AS RRelationships_Resluts, Relationship_Change = R.Relationships_Results - F.Relationships_Results
FROM First_basis AS F
FULL Outer JOIN RECENT_BASIS AS R
ON F.ClientKey = R.ClientKey AND F.ProgramAdmitKey = R.ProgramAdmitKey
ORDER BY F.ClientKey
END
GO