Complex SQL selection query - sql

Question

I have a stored procedure which needs a different if condition to work properly.
The procedure has 2 parameter namely, #CategoryID and #ClassID, which basically come from a UI tree view functionality. #CategoryID corresponds to the parent nodes, while #ClassID corresponds to the child nodes.
Based upon the above parameters I need to make a selection(Column Code) from a table which has CategoryID and ClassID as columns.
Now there are 2 scenarios:
Scenario 1
#CategoryID:A
#ClassID:B (which is a child node of CategoryID A)
Result needed: Codes corresponding to only ClassID B, which is basically the intersection
Scenario 2
#CategoryID:A
#ClassID: C (which is not a child node for CategoryID A)
Result needed: Codes corresponding to the CategoryID A, as well as ClassID B, basically a union
The procedure which I wrote gives me correct answer for the second scenario, but the first scenario it fails. Below is my procedure:
ALTER PROCEDURE [dbo].[uspGetCodes]
#CategoryID varchar(50),
#ClassID varchar(50)
AS
BEGIN
BEGIN TRY
DECLARE #SQLQuery NVARCHAR(MAX)
SET #SQLQuery=N'SELECT Code FROM dbo.ClassToCategoryMapping WHERE '
IF (#CategoryID IS NULL OR #CategoryID='')
BEGIN
SET #SQLQuery=#SQLQuery + 'ClassId IN ('+#ClassID+')'
PRINT(#SQLQuery)
EXEC(#SQLQuery)
END
ELSE IF (#ClassID IS NULL OR #ClassID='')
BEGIN
SET #SQLQuery=#SQLQuery+'CategoryID IN ('+#CategoryID+')'
PRINT(#SQLQuery)
EXEC(#SQLQuery)
END
ELSE
BEGIN
SET #SQLQuery=#SQLQuery+'(CategoryID IN ('+#CategoryID+') OR ClassId IN ('+#ClassID+') )'
PRINT(#SQLQuery)
EXEC(#SQLQuery)
END
END TRY
BEGIN CATCH
SELECT ERROR_NUMBER() AS 'ErrorNumber', ERROR_MESSAGE() AS 'ErrorMessage', ERROR_SEVERITY() AS 'ErrorSeverity', ERROR_STATE() AS 'ErrorState', ERROR_LINE() AS 'ErrorLine'
RETURN ERROR_NUMBER()
END CATCH
END
The Last Else part actually does an 'OR', which gives me the union of the Codes for CategoryID's and ClassID's irrespective whether the given ClassID is a child of the given CategoryID or not.
My question over here would be, how to write the condition to achieve both the scenarios.
Latest Sample Data:
Scenario 1
#CategoryId=2,5, #ClassID=10 (Here 10 is the child while 2 is the parent, CategoryID 2 corresponds to ClassID's 10, 11, 12)
Expected Result: 10, 26, 27 (26 and 27 correspond to the CategoryID 5)
Scenario 2
#CategoryID=2, #ClassID=13,15 (13 and 15 is the child of a different parent, CategoryID 2 corresponds to ClassID's 10, 11 ,12)
Expected Result: 10, 11, 12, 13, 15
Data in Table dbo.ClasstoCategoryMapping will be somewhat as below:
CategoryID ClassID Code
2 10 200
2 11 201
2 12 202
5 26 501
5 27 502
6 15 601
6 16 602
6 17 603
7 20 701
7 21 702
7 22 703
I guess I have made my question quite clear, if no then, folks can ask me to edit it. I would be happy to do so. I urge the experts to assist me in this problem. Any pointers too will be quite appreciated.
Regards
Anurag

Answer 1

If I understand the question correctly, what you require in your result set is:
(all supplied classid) + (all classid for supplied categoryid with no matching supplied classid)
That would translate to the following:
CREATE PROCEDURE [dbo].[uspGetCodes]
(
#CategoryID varchar(50),
#ClassID varchar(50)
)
AS
BEGIN
SELECT COALESCE(CM.CategoryID, CM2.CategoryID) AS CategoryID,
COALESCE(CM.ClassID, CM2.ClassID) AS ClassID,
COALESCE(CM.Code, CM2.Code) AS Code
--Matched classIDs:
FROM dbo.udfSplitCommaSeparatedIntList(#ClassID) CLAS
JOIN dbo.ClassToCategoryMapping CM
ON CM.ClassId = CLAS.Value
--Unmatched CategoryIDs:
FULL
OUTER
JOIN dbo.udfSplitCommaSeparatedIntList(#CategoryID) CAT
ON CM.CategoryID = CAT.Value
LEFT
JOIN dbo.ClassToCategoryMapping CM2
ON CM.CategoryID IS NULL
AND CM2.CategoryID = CAT.Value
END
I have included Category, Class and Code in the result since its easier to see what's going on, however I guess you only really need code
This makes use of the following function to split the supplied comma separated strings:
CREATE FUNCTION [dbo].[udfSplitCommaSeparatedIntList]
(
#Values varchar(50)
)
RETURNS #Result TABLE
(
Value int
)
AS
BEGIN
DECLARE #LengthValues int
SELECT #LengthValues = COALESCE(LEN(#Values), 0)
IF (#LengthValues = 0)
RETURN
DECLARE #StartIndex int
SELECT #StartIndex = 1
DECLARE #CommaIndex int
SELECT #CommaIndex = CHARINDEX(',', #Values, #StartIndex)
DECLARE #Value varchar(50);
WHILE (#CommaIndex > 0)
BEGIN
SELECT #Value = SUBSTRING(#Values, #StartIndex, #CommaIndex - #StartIndex)
INSERT #Result VALUES (#Value)
SELECT #StartIndex = #CommaIndex + 1
SELECT #CommaIndex = CHARINDEX(',', #Values, #StartIndex)
END
SELECT #Value = SUBSTRING(#Values, #StartIndex, LEN(#Values) - #StartIndex + 1)
INSERT #Result VALUES (#Value)
RETURN
END

Answer 2

this is the sample query that can achieve your goal, is this what you want?
DECLARE #SAMPLE TABLE
(
ID INT IDENTITY(1,1),
CategoryId INT,
ClassID INT
)
INSERT INTO #sample
VALUES(2,10)
INSERT INTO #sample
VALUES(2,11)
INSERT INTO #sample
VALUES(2,12)
INSERT INTO #sample
VALUES(3,13)
DECLARE #CategoryID INT
DECLARE #ClassID Int
--Play around your parameter(s) here
SET #CategoryID = 2
SET #ClassID = 13
--Snenario 1
--#CategoryId=2, #ClassID=10 (Here 10 is the child while 2 is the parent, CategoryID 2 corresponds to ClassID's 10, 11, 12)
--Expected Result: 10
IF EXISTS(SELECT * FROM #SAMPLE WHERE CategoryId = #CategoryID AND ClassID = #ClassID)
SELECT ClassID FROM #SAMPLE WHERE CategoryId = #CategoryID AND ClassID = #ClassID
--Scenario 2
--#CategoryID=2, #ClassID=13 (13 is the child of a different parent, CategoryID 2 corresponds to ClassID's 10, 11 ,12)
--Expected Result: 10, 11, 12, 13
ELSE
SELECT ClassID FROM #SAMPLE WHERE ClassID = #ClassID OR CategoryId = #CategoryID

Answer 3

Try this
select * from yourtable
where CategoryId = #CategoryID and ClassID = #ClassID
union
select * from
(
select * from yourtable where ClassID = #ClassID
union
select * from yourtable where CategoryId = #CategoryID
) v
where not exists (select * from yourtable where CategoryId = #CategoryID and ClassID = #ClassID)

Answer 4

UPDATE FOR DELIMITED STRING
If you have a comma delimited string then it is best to use a CLR function to create the table, but you could use a SQL function. Examples of how to do this are easy to find with a Google search... but for reference here is one good article on the subject -> http://www.sqlperformance.com/2012/07/t-sql-queries/split-strings I expect at some point there will be native support on most platforms.
Given that you have a function that returns a table of one column (named ID) of type int, or an empty table on a null input. Note: You may have to have the null return a table with one row containing an invalid value (a value that will never join), say -1.
The code is as simple as this:
SELECT Code
FROM ClassToCategoryMapping
LEFT JOIN MakeTableFromCVS(#CategoryID) AS CatTable
ON CatTable.ID = CategoryID
LEFT JOIN MakeTableFromCVS(#ClassID) AS ClassTable
ON ClassTable.ID = ClassID
WHERE
CASE
WHEN #CatgoryID IS NULL THEN -1 ELSE CatTable.ID
END = ISNULL(CatTable.ID,-1)
AND
CASE
WHEN #ClassID IS NULL THEN -1 ELSE ClassTable.ID
END = ISNULL(ClassTable.ID,-1)
AND
COALESCE(CatTable.ID,ClassTable.ID,-1) != -1
The logic is the same as below. Because the join will vary the values if it is not null we have to use a different trick. Here we use a marker value (in this case -1) to signal the null value. Any value that won't appear in the comma separated list will work as this marker value, remember it must be of the same type.
You don't need dynamic SQL here and you will find SQL server is better at optimizing if you don't use dynamic SQL. In fact, you don't even need an if statement If you can be sure the input is always null you can do this:
SELECT Code
FROM ClassToCategoryMapping
WHERE
How this works
This query checks for both CategoryID and ClassID columns match the incoming parameters but "ignores" the input when they are null by checking the column against itself. This is an handy SQL trick.
Note if you do need to check for empty strings then this will be almost as fast
DECLARE #myCatID varchar(max)
DECLARE #myClassID varchar(max)
SET #myCatID = #CategoryID
SET #myClassID = #ClassID
IF LTRIM(RTRIM(#CategoryID) = '' THEN SET #myCatID = NULL
IF LTRIM(RTRIM(#ClassID) = '' THEN SET #myClassID = NULL
SELECT Code
FROM ClassToCategoryMapping
WHERE CatgoryID = ISNULL(#myCatID,CategoryID)
AND ClassID = ISNULL(#myClassID,ClassID)
You can replace ISNULL() with COALESCE() if you want... they do the same thing in this case.