Microsoft SQL Case statement not working in Order By statement - sql-server

Question

I have a database column which is used as a grouping for variations for products and it is not in the First Normal Form. We don't need the Width, Height and the measurements to be in separate columns.
We have various attributes in this one database column, for example, product sizes like 1200*400mm and sometimes meters like 1m or even colors like red, blue and green.
The issue is that the CASE statement is being ignored and SQL is trying to Convert Black to an Int in the Case statement.
Currently the code needs to Sort the sizes correctly which the SQL now does. The issue comes in when it fetches a product with only colour attributes and the CASE statement is ignored near the Order By section.
I have created this SQL Fiddle to showcase the DB column with Sizes and Colors.
http://sqlfiddle.com/#!18/4e58e/1
This is my current SQL:
DECLARE #StockID int = 684
DECLARE #VariationParent int = (SELECT TOP 1 StockParent_ParentId FROM
StockVariations SV INNER JOIN FinGoodsParent FGP ON FGP.Id =
SV.StockParent_ChildId WHERE StockParent_ChildId = #StockID AND
SV.IsDeleted = 0 AND FGP.IsDeleted = 0 AND FGP.Publish = 1)
SELECT AV.ID, AV.AttrValue, AV.AttributeTypes_Id 'AttributeTypeID',
CAST(CASE WHEN SA.StockParent_Id = #StockID THEN 1 ELSE 0 END as BIT)
'IsDefault'
FROM AttributeTypes AT
INNER JOIN AttributeValues AV ON AV.AttributeTypes_Id = AT.Id
INNER JOIN StockParent_AttributeValues SA on SA.AttributeValue_Id = AV.Id
INNER JOIN FinGoodsParent FGP ON FGP.Id = SA.StockParent_Id AND
FGP.IsDeleted = 0 AND FGP.Publish = 1
WHERE SA.StockParent_Id IN (SELECT SV.StockParent_ChildId FROM
StockVariations SV INNER JOIN FinGoodsParent FGP ON FGP.Id =
SV.StockParent_ChildId AND FGP.IsDeleted = 0 AND FGP.Publish = 1 WHERE
SV.StockParent_ParentId = #VariationParent AND SV.IsDeleted = 0)
AND SA.IsDeleted = 0 AND AT.IsDeleted = 0 AND AV.IsDeleted = 0
ORDER BY
CASE WHEN (CHARINDEX('*', AV.AttrValue) > 0
AND CHARINDEX('mm', AV.AttrValue) > 0)
THEN
CONVERT(int, (select top 1 value from STRING_SPLIT(AV.AttrValue, '*'))) *
CONVERT(int, (select top 1 LEFT(value, LEN(value) - 2) from
STRING_SPLIT(AV.AttrValue, '*') where value LIKE '%mm'))
ELSE
AV.AttrValue
END
ASC
This is the error I am getting when trying to fetch a product with only color attributes and sorting it by the Attribute name with the CASE Statement.
So basically I got this SQL code to do the sorting from How to match a width and height size with a Regex expression and use Sort By in SQL or C# to build a drop-down?
I have added the CASE statement to try and only do the sorting when there is an Asterisk * and mm in the column, otherwise, I would just like to use Order By attrValue normally when the column contains, for example, red or black instead of numerics.
Updated
I have updated the SQL Fiddle as the data Output should only be either Sizes or Colours. So I have added an additional column with a type for this example. The SQL retrieving the data near the WHERE Clause should be either 0 for sizes or 1 for just colors and the SQL should still be able to work and order the Output of the sizes correctly.
http://sqlfiddle.com/#!18/56b3e/1

Answer 1

Explanations:
Consider the following:
CASE evaluates a list of conditions and returns the highest precedence type from the set of types. In your case you have int and varchar as possible return values and this explains your Conversion failed when converting the varchar value 'Black' to data type int error.
do not use SELECT TOP 1 FROM STRING_SPLIT() because STRING_SPLIT() doesn't guarantee that the order of the splitted substrings matches their positions in the original string. In your case you may try to use simple string parsing with LEFT, RIGHT and CHARINDEX functions. After that you need to convert the result from calculations to varchar.
Example:
Table:
CREATE TABLE attributes
([AttrValue] varchar(13))
;
INSERT INTO attributes
([AttrValue])
VALUES
('900*900mm'),
('1200*900mm'),
('1200*1200mm'),
('1200*6000mm'),
('1500*3000mm'),
('Red'),
('Green'),
('Black'),
('Purple')
;
Statement:
SELECT
AttrValue
FROM
attributes
ORDER BY
CASE
WHEN (CHARINDEX('*', AttrValue) > 0 AND CHARINDEX('mm', AttrValue) > 0) THEN
RIGHT(
REPLICATE('0', 13) +
CONVERT(
varchar(13),
CONVERT(int, LEFT(REPLACE(AttrValue, 'mm', ''), CHARINDEX('*', REPLACE(AttrValue, 'mm', '')) - 1)) *
CONVERT(int, RIGHT(REPLACE(AttrValue, 'mm', ''), LEN(REPLACE(AttrValue, 'mm', '')) - CHARINDEX('*', REPLACE(AttrValue, 'mm', ''))))
),
13
)
ELSE AttrValue
END ASC
Output:
--------------
AttrValue
--------------
900*900mm
1200*900mm
1200*1200mm
1500*3000mm
1200*6000mm
Black
Green
Purple
Red