Manipulating SQL table - sql

Question

I have a table, the structure of which I have simplified to the smaller table below.
I want to manipulate the dataset below into the following form:
The new dataset will contain a single record for each case of DC, with a yes/no flag indicating if the NatureOfTumour has changed from DC to IN, and the time taken to change from DC to IN if applicable.
The change from DC to IN will be considered only if location has remained the same i.e. only those records should be considered where NatureOfTumour has changed from DC to IN and the location remained the same. ItemNo is the unique ID.
On a community member's advice I have pasted the table in text below as well, cleaned up as best as I could. The last column "Gen" is empty. ItemNo is the unique ID. Copying the text below to excel and doing a text-to-columns (separated by spaces) should give you the original table in a readable format. Sorry cant think of a better way to paste the table here.
ItemNo DateOfTest NatureOfTumour Location Centre Gen
2345 07/2006 DC P S-224
2345 12/2006 IN P S-224
2342 05/2004 DC Q B-266
3878 06/2006 DC P S-224
3878 05/2005 DC Q S-224
5678 09/2000 IN P S-224
5597 10/2001 DC P B-266
5597 01/1999 IN Q B-266

Answer 1

Try this. The LEAD function looks at the next row based on groups of ItemNo ordered by DateOfTest.
WITH abc AS (
SELECT
ItemNo
,DateOfTest
,NatureOfTumour
,Location
,Centre
,LEAD(NatureOfTumour) OVER (PARTITION BY ItemNo ORDER BY DateOfTest) as FutureNature
,LEAD(Location) OVER (PARTITION BY ItemNo ORDER BY DateOfTest) as FutureLocation
,LEAD(DateOfTest) OVER (PARTITION BY ItemNo ORDER BY DateOfTest) as FutureDateOfTest
FROM test_results
)
SELECT
ItemNo
,DateOfTest
,NatureOfTumour
,CASE
WHEN FutureNature = 'IN'
AND FutureLocation = Location
THEN 'Yes'
ELSE 'NO'
END AS State_Change
,FutureDateOfTest - DateOfTest as Date_Diff
,Location
,Centre
from abc
WHERE NatureOfTumour = 'DC'

Answer 2

You need a self join. Something along these lines:
SELECT
d.ItemNo,
i.DateOfTest - d.DateOfTest AS datediff,
d.Location,
d.Centre,
d.Gen
FROM
(
SELECT
*
FROM demo
WHERE NatureOfTumour = 'DC'
) d
INNER JOIN
(
SELECT
*
FROM demo
WHERE NatureOfTumour = 'IN'
) i ON d.ItemNo = i.ItemNo
AND d.Location = i.Location;

Answer 3

If I understood your question, you could try this:
Let me know .
If you want in output only the rows who changed (GEN='Y'), change LEFT JOIN to INNER JOIN.
SELECT A.ITEMNO, A.DATEOFTEST, A.NATUREOFTUMOUR, A.LOCATION
, CASE WHEN B.NATUREOFTUMOUR='IN' AND A.LOCATION = B.LOCATION THEN 'Y' ELSE 'N' END AS GEN_NEW
, CASE WHEN B.NATUREOFTUMOUR='IN' AND A.LOCATION = B.LOCATION THEN B.DATEOFTEST-A.DATEOFTEST END AS TIME_PASS
FROM TE A
LEFT JOIN TE B ON A.ITEMNO=B.ITEMNO AND B.NATUREOFTUMOUR<>'DC' AND A.DATEOFTEST < B.DATEOFTEST
WHERE A.NATUREOFTUMOUR='DC
OR (I can't understand from your question)
SELECT A.ITEMNO, A.DATEOFTEST, A.NATUREOFTUMOUR, A.LOCATION
, CASE WHEN B.NATUREOFTUMOUR='IN' THEN 'Y' ELSE 'N' END AS GEN_NEW
, CASE WHEN B.NATUREOFTUMOUR='IN' THEN B.DATEOFTEST-A.DATEOFTEST END AS TIME_PASS
FROM TE A
LEFT JOIN TE B ON A.ITEMNO=B.ITEMNO AND B.NATUREOFTUMOUR<>'DC' AND A.DATEOFTEST < B.DATEOFTEST AND A.LOCATION = B.LOCATION
WHERE A.NATUREOFTUMOUR='DC'\\
Output
ITEMNO DATEOFTEST NATUREOFTUMOUR LOCATION GEN_NEW TIME_PASS
1 2345 01.07.2006 DC P Y 153
2 2342 01.06.2006 DC Q N NULL
3 5597 01.10.2001 DC P N NULL
4 3878 01.05.2005 DC Q N NULL
5 3878 01.06.2006 DC P N NULL