1. Improving Overlap Based on Expected Value
By: Joo Li Lee

2. STEP 1: CLEAN TABLE
SELECT [ID]
,Cast([Cancer] as float) Cancer
,[I305 1] I305_1
,[I309 81] I309_81
,[I311 ] I311
,[IE849 7] IE849_7
,[I150 9] I150_9
,[I276 1] I276_1
,[I276 8] I276_8
,[I530 81] I530_81
,[I263 9] I263_9
,[I276 51] I276_51
,[IV15 82] IV15_82
,[I511 9] I511_9
,[I401 9] I401_9
,[I787 20] I787_20
,[I564 00] I564_00
,[I272 4] I272_4
,[I280 9] I280_9
,[I285 9] I285_9
,[I496 ] I496
,[I458 9] I458_9
,[I486 ] I486
,[IV58 61] IV58_61
,[I197 7] I197_7
,[I578 9] I578_9
,[I584 9] I584_9
,[IV66 7] IV66_7
,[I244 9] I244_9
,[I414 01] I414_01
,[I599 0] I599_0
,[I414 00] I414_00
,[I585 9] I585_9
,[I600 00] I600_00
,[I428 0] I428_0
,[I427 31] I427_31
,[I403 90] I403_90
,Cast([Dead] as float) Dead
into StomachCancer_Table
FROM [HAP823].[dbo].[StomachCancer]
This code shows cleaning the table name StomachCancer

3. STEP 2: CREATING STRATA
DROP TABLE #STRATA_TABLE SELECT ID ,Cancer ,Dead ,[I150_9]+[I197_7]+[I244_9]+[I263_9]+[I272_4]+[I276_1]+[I276_51]+[I276_8]+[I280_9] +[I285_9]+[I305_1]+[I309_81]+[I311]+[I401_9]+[I403_90]+[I414_00]+[I414_01]+[I427_31] +[I428_0]+[I458_9]+[I486]+[I496]+[I511_9]+[I530_81]+[I564_00]+[I578_9]+[I584_9] +[I585_9]+[I599_0]+[I600_00]+[I787_20]+[IE849_7]+[IV15_82]+[IV58_61]+[IV66_7]Strata INTO #STRATA_TABLE FROM StomachCancer_Table ORDER BY STRATA;
Creating strata by concatenating the independent variables

4. STEP 4: CREATING CONTROLS
STEP 3: CREATING CASES
STEP 4: CREATING CONTROLS
DROP TABLE #CASES Select Count (distinct ID) as nCases ,SUM(IIF(Dead = 1, 1., 0.)) as a ,SUM(IIF(Dead = 0, 1., 0.)) as b ,STRATA INTO #Cases FROM #STRATA_TABLE WHERE CANCER = 1 GROUP BY STRATA
DROP TABLE #CONTROLS
Select Count (distinct ID) as nControls
,SUM(IIF(Dead = 1, 1., 0.)) as c
,SUM(IIF(Dead = 0, 1., 0.)) as d
,STRATA
INTO #Controls
FROM #STRATA_TABLE
WHERE CANCER = 0
GROUP BY STRATA

5. STEP 5: INNER JOIN – FIND CASES WITH MATCHES
DROP TABLE #MATCH SELECT Round(Cast([nCases] as float)/Cast([nControls] as float),2) As [Weight] ,nControls ,c -- no cancer & dead ,d -- no cancer & not dead ,#Cases.* INTO #MATCH FROM #Cases JOIN #Controls On #Cases.Strata = #Controls.STRATA ORDER BY [WEIGHT]

6. STEP 5.1: CALCULATING OVERLAP
AS FLOAT
= (SELECT SUM(nCases) FROM #Cases)
SELECT as overlap
FROM #MATCH
-- Overlap :
Using the partial matching method, we are going to increase this overlap.

7. STEP 6: LEFT JOIN – FIND CASES WITH NO MATCH
DROP TABLE #MATCH_LEFT
/*Left Join*/
SELECT ROW_NUMBER() OVER (ORDER BY #Cases.STRATA DESC) as ID
,'0' STRATA_SET
,Round(Cast([nCases] as float)/Cast([nControls] as float),2) As [Weight]
,nControls
,c -- no cancer & dead
,d -- no cancer & not dead
,#Cases.*
INTO #MATCH_LEFT
FROM #Cases LEFT JOIN #Controls
On#Cases.Strata = #Controls.STRATA
SELECT * FROM #MATCH_LEFT

8. STEP 6.1: CREATING TWO TABLES (MATCHED AND NOT MATCHED)
DROP TABLE #MATCH_NULL
SELECT *
INTO #MATCH_NULL Match NULL
FROM #MATCH_LEFT WHERE [WEIGHT] IS NULL
--(96 rows affected)
DROP TABLE #MATCH_NOT_NULL
INTO #MATCH_NOT_NULL Match NOT NULL
FROM #MATCH_LEFT WHERE [WEIGHT] IS NOT NULL
--(84 rows affected)
Insert cases that did NOT match into table #MATCH_NULL
Insert cases that did match into table #MATCH_NOT_NULL

9. STEP 6.2: CREATING STRATA TABLE FOR CONTROLS
DROP TABLE #CONTROLS_STRATA
SELECT nControls, c, d
,STRATA
,RIGHT(STRATA, LEN(STRATA) -1) STRATA_1
,RIGHT(STRATA, LEN(STRATA) -2) STRATA_2
,RIGHT(STRATA, LEN(STRATA) -3) STRATA_3
,RIGHT(STRATA, LEN(STRATA) -4) STRATA_4
,RIGHT(STRATA, LEN(STRATA) -5) STRATA_5
,RIGHT(STRATA, LEN(STRATA) -6) STRATA_6
,RIGHT(STRATA, LEN(STRATA) -7) STRATA_7
,RIGHT(STRATA, LEN(STRATA) -8) STRATA_8
,RIGHT(STRATA, LEN(STRATA) -9) STRATA_9
,RIGHT(STRATA, LEN(STRATA) -10) STRATA_10
INTO #CONTROLS_STRATA
FROM #Controls
This part of the code is creating new columns by dropping one diagnosis every time the number is decreasing

10. STEP 6.3: CREATING STRATA TABLE FOR CASES
DROP TABLE #Cases_STRATA
SELECT ID
, nCases, a, b
,RIGHT(STRATA, LEN(STRATA) -1) STRATA_1
,RIGHT(STRATA, LEN(STRATA) -2) STRATA_2
,RIGHT(STRATA, LEN(STRATA) -3) STRATA_3
,RIGHT(STRATA, LEN(STRATA) -4) STRATA_4
,RIGHT(STRATA, LEN(STRATA) -5) STRATA_5
,RIGHT(STRATA, LEN(STRATA) -6) STRATA_6
,RIGHT(STRATA, LEN(STRATA) -7) STRATA_7
,RIGHT(STRATA, LEN(STRATA) -8) STRATA_8
,RIGHT(STRATA, LEN(STRATA) -9) STRATA_9
,RIGHT(STRATA, LEN(STRATA) -10) STRATA_10
INTO #CASES_STRATA
FROM #MATCH_NULL
This part of the code is creating new columns by dropping one diagnosis every time the number is decreasing

11. STEP 7: DROPPING ONE ATTRIBUTE AT A TIME – FINDING LONGEST MATCH FOR CASES THAT HAD NO MATCH
DROP TABLE #MATCH_1
SELECT DISTINCT ID, '1' STRATA_SET
,round(CAST([nCases] as float)/Cast([nControls] as float),2) [Weight]
,nControls
,t2.c ,t2.d
,nCases
,a,b
,t1.STRATA_1 STRATA
INTO #MATCH_1
FROM #CASES_STRATA t1 LEFT JOIN #CONTROLS_STRATA t2
on t1.STRATA_1 = T2.STRATA_1
DROP TABLE #MATCHED_NULL
SELECT *
INTO #MATCHED_NULL
FROM #MATCH_1
WHERE [WEIGHT] IS NOT NULL

12. STEP 7.1: DROPPING ANOTHER ATTRIBUTE – FINDING LONGEST MATCH FOR CASES THAT HAD NO MATCH DURING FIRST ATTRIBUTE DROP
DROP TABLE #MATCH_2
SELECT DISTINCT ID
,'2' STRATA_SET
,round(CAST(SUM([nCases]) as float)/Cast(SUM([nControls]) as float),2) [Weight]
,SUM(nControls) nControls
,SUM(t2.c) C,SUM(t2.d) D
,SUM(nCases) nCases,SUM(a) A,SUM(b) B,t1.STRATA_2 STRATA
INTO #MATCH_2
FROM #CASES_STRATA t1 LEFT JOIN #CONTROLS_STRATA t2
on t1.STRATA_2 = T2.STRATA_2
WHERE ID NOT IN (SELECT ID FROM #MATCHED_NULL)
GROUP BY ID,t1.STRATA_2
INSERT INTO #MATCHED_NULL
SELECT *
FROM #MATCH_2
WHERE [WEIGHT] IS NOT NULL

13. CONTINUE DROPPING ATTRIBUTES

14. STEP 8: CREATING A FINAL TABLE TO ANALYZE ON
DROP TABLE #FINAL
SELECT *
INTO #FINAL
FROM #MATCH_NOT_NULL
INSERT INTO #FINAL
SELECT * FROM #MATCHED_NULL
SELECT * FROM #FINAL
The #MATCH_NOT_NULL table contains the cases that matched from the beginning.
The #MATCH_NULL table contains cases where matches were found by dropping attributes one by one.
All the matched cases are in the table #FINAL. Table #FINAL will be used to analyze the improved overlap

15. STEP 8.1: CALCULATING OVERLAP
AS FLOAT
= (SELECT SUM(nCases) FROM #Cases)
SELECT AS overlap
FROM #FINAL
Type
Overlap
Original
Dropped up to 7 Attributes