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Stairway to T-SQL: Beyond The Basics Level 6: Using the CASE Expression and IIF Function


Stairway to T-SQL: Beyond The Basics Level 6: Using the CASE Expression and IIF Function

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Greg Larsen
Greg Larsen
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Comments posted to this topic are about the item Stairway to T-SQL: Beyond The Basics Level 6: Using the CASE Expression and IIF Function

Gregory A. Larsen, MVP
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Thanks Greg, good stuff! I like the addition of IIF in 2012. :-)
jagsalog
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Thank you, very helpful.

In a large development, I would use a only on CASE rather than IIF for readability and uniformity.
Mike Dougherty-384281
Mike Dougherty-384281
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I was surprised you didn't discuss case inside aggregate functions.

before PIVOT existed we used something like this:
select
entityid
,fieldA = max( case when attribute="A" then value else '' end )
,fieldB = max( case when attribute="B" then value else '' end )
,...
,fieldN = max( case when attribute="N" then value else '' end )
from
EAVtable
group by
entityid

I've also used case for custom group/order by:
order by
case @tcSortField
when "LastName" then person.LastName
when "Email" then person.EmailAddress
etc.
end
webrunner
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Thanks for the great article!

I just want to make one small comment. I ran the code below:

SELECT OrderAmt,
IIF(OrderAmt > 200,
'High $ Order',
'Low $ Order') AS OrderType
FROM MyOrder;


and got this error:

Msg 102, Level 15, State 1, Line 2
Incorrect syntax near '>'.

When I Googled the error, it turns out IIF() is not implemented in SQL 2008. I didn't see that noted in the article so it would be helpful to add a note about that at the start of the piece.

But again, this is a fantastic tutorial! Thanks again!

- webrunner

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Hello,
In your Stairway to T-SQL Beyond The Basics Level 6 Using the CASE Expression and IIF Function covering the Listing 7: Nesting CASE statement lesson. If I was to add to your “MyOrder” table the values;
('01-15-2015', 301.00,NULL), and then run your code, the result for my added value would return. Meaning that if the OrderAmt_Category is Null it would be a layaway. I would think that it should be without layaway.

301.00 NULL 300 Dollar Order with Layaway
USE tempdb
GO
SELECT OrderAmt, Layaway,
CASE
WHEN OrderAmt < 100 THEN '< 100 Dollar Order'
WHEN OrderAmt < 200 THEN '100 Dollar Order'
WHEN OrderAmt < 300 THEN
CASE
WHEN Layaway = 'N'
THEN '200 Dollar Order without Layaway'
ELSE '200 Dollar Order with Layaway' END
ELSE
CASE
WHEN Layaway = 'N'
THEN '300 Dollar Order without Layaway'
ELSE '300 Dollar Order with Layaway' END
END AS OrderAmt_Category
FROM MyOrder
order by OrderAmt;

-----------Reorder/Change the 2nd and 3rd CASE statements to accomodate the "Null" values correctly
USE tempdb
GO
SELECT OrderAmt, Layaway,
CASE
WHEN OrderAmt < 100 THEN '< 100 Dollar Order'
WHEN OrderAmt < 200 THEN '100 Dollar Order'
WHEN OrderAmt < 300 THEN
CASE
WHEN Layaway = 'Y'
THEN '200 Dollar Order with Layaway'
ELSE '200 Dollar Order without Layaway' END
ELSE
CASE
WHEN Layaway = 'Y'
THEN '300 Dollar Order with Layaway'
ELSE '300 Dollar Order without Layaway' END
END AS OrderAmt_Category
FROM MyOrder
order by OrderAmt;

Great article and very helpful
kwoznica
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Nice article Greg.

I've had to use CASE expressions quite often recently in a data migration from an old ERP system.

You not only just taught me a few new tricks but answered lingering questions I had on why some results are returned.
Iwas Bornready
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Good basic info about CASE. I've never used IIF, always just CASE.
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