I'm trying to Create a stored procedure but there is a field actually exist in another field but its id is used as foreign key in current table, SQL Query is:
Create Procedure sp_Select
As
Begin
SELECT [ProductID]
,[Name]
,SELECT tblCategories.CategoryName
FROM tblCategories INNER JOIN tblProducts
ON tblCategories.CategoryId = tblProducts.CategoryID;
,[Model]
,Cast([RAM] As nvarchar(10)) +' '+[RAMMemUnit] As RAM
,Cast([SecondryMem] As nvarchar(10)) + ' ' + [SecondMemUnit] As Memory
,[OSVersion]
,[Processor]
,CAST([Battery] As nvarchar(10)) +' '+ [BatteryType] As Battery
,UnitsInStock AS 'Quantity In Stock'
FROM [tblProducts]
End
Error in this following portion:
SELECT tblCategories.CategoryName FROM tblCategories INNER JOIN tblProducts ON tblCategories.CategoryId = tblProducts.CategoryID;
Someone help me please.
1 Answer 1
There are actually two problems with your first query. The first is that you have an extra semi-colon for the subquery where you are getting the category name. The second is that if that query returns more than one row then you will receive an error. I've corrected it for you to eliminate both of those issues.
CREATE PROCEDURE sp_Select
AS
BEGIN
SELECT [ProductID]
,[Name]
, CategoryName = (SELECT TOP 1 tblCategories.CategoryName
FROM tblCategories
WHERE tblCategories.CategoryId = tblProducts.CategoryID)
,[Model]
, Cast([RAM] AS NVARCHAR(10)) + ' ' + [RAMMemUnit] AS RAM
,Cast([SecondryMem] AS NVARCHAR(10)) + ' ' + [SecondMemUnit] AS Memory
,[OSVersion]
,[Processor]
,CAST([Battery] AS NVARCHAR(10)) + ' ' + [BatteryType] AS Battery
,UnitsInStock AS 'Quantity In Stock'
FROM [tblProducts];
END
However, queries that have sub-queries like the above generally perform worse than ones that can achieve the same results with a sub-query. It lets you access other fields from the tblCategories table without incurring additional sub-query costs, and you can more easily search for products that are in particular categories.
Some of the comments have mentioned changing the join from using a LEFT OUTER to be an INNER join. I chose LEFT OUTER initially because that more closely matched the result set you would have received in your first query. Essentially, it would have NULL's in place where the CategoryName would be assuming you had Products without Categories. An INNER JOIN would eliminate products that had no matching category.
CREATE PROCEDURE sp_Select
AS
BEGIN
SELECT P.[ProductID]
,P.[Name]
, C.CategoryName
,P.[Model]
, Cast(P.[RAM] AS NVARCHAR(10)) + ' ' + P.[RAMMemUnit] AS RAM
,Cast(P.[SecondryMem] AS NVARCHAR(10)) + ' ' + P.[SecondMemUnit] AS Memory
,P.[OSVersion]
,P.[Processor]
,CAST(P.[Battery] AS NVARCHAR(10)) + ' ' + P.[BatteryType] AS Battery
,P.UnitsInStock AS 'Quantity In Stock'
FROM [tblProducts] AS P
LEFT OUTER JOIN tblCategories AS C ON C.CategoryId = P.CategoryID;
END
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1I don't think there's any guarantee that replacing a subquery with a left outer join will make things faster.Erik Reasonable Rates Darling– Erik Reasonable Rates Darling2017年03月29日 02:55:12 +00:00Commented Mar 29, 2017 at 2:55
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The corrected subquery needs more correction: to become correlated. As it is, it will return more than 1 rows and throw error (unless there is only 1 product).ypercubeᵀᴹ– ypercubeᵀᴹ2017年03月29日 07:51:46 +00:00Commented Mar 29, 2017 at 7:51
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So Can you please correct it.?Muhazzab Chouhadry– Muhazzab Chouhadry2017年03月29日 11:14:13 +00:00Commented Mar 29, 2017 at 11:14
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@MuhazzabChouhadry - The final query deals with it, by removing the subquery. The
INNER JOIN
provides the correlation mentioned. If you really want to use the subquery, replaceINNER JOIN tblProducts ON
withWHERE
in the first version of the query in Jonathan's answer.RDFozz– RDFozz2017年03月29日 18:34:36 +00:00Commented Mar 29, 2017 at 18:34 -
@RDFozz I think this is also working fine, What is the benefit of using this query.?Muhazzab Chouhadry– Muhazzab Chouhadry2017年03月30日 03:11:55 +00:00Commented Mar 30, 2017 at 3:11