Output of Query

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Output of Query

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Stuart Davies SSCoach Points: 19271 More actions · Answer 1

Nice question - thanks

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Sean Lange SSC Guru Points: 286562 More actions · Answer 2

sqlzealot-81 (10/10/2011)
I guess, you can achieve by the below way,
SELECT
CASE IsNull(COL1,'') WHEN '' THEN 'Is Null'
WHEN '0' THEN 'Is Zero'
WHEN '1' THEN 'Is One'
WHEN '2' THEN 'Is Two'
END
FROM
(
SELECT NULL AS Col1
UNION
SELECT '0' AS Col1
UNION
SELECT '1' AS Col1
UNION
SELECT '2' AS Col1
) TMP

This works except you can't differentiate between null and empty strings because your isnull will now treat them both the same. In some cases this is ok but in others it isn't.

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BarbW SSCarpal Tunnel Points: 4759 More actions · Answer 3

I got an error when I executed the code - oh well :hehe:

Toreador SSChampion Points: 11299 More actions · Answer 4

Sean Lange (10/10/2011)[hrThis works except you can't differentiate between null and empty strings because your isnull will now treat them both the same. In some cases this is ok but in others it isn't.

If it matters then you can do something like

CASE IsNull(COL1,'avaluethatwillnotappearinthedata') WHEN 'avaluethatwillnotappearinthedata' THEN 'Is Null'

Toreador SSChampion Points: 11299 More actions · Answer 5

Or:

SELECT

CASE when Col1 is null then 'Is Null'

else case col1

WHEN '0' THEN 'Is Zero'

WHEN '1' THEN 'Is One'

WHEN '2' THEN 'Is Two'

END

end

FROM

(

SELECT NULL AS Col1

UNION

SELECT '0' AS Col1

UNION

SELECT '1' AS Col1

UNION

SELECT '2' AS Col1

) TMP

SQLRNNR SSC Guru Points: 281324 More actions · Answer 6

Thanks for the question.

Jason...AKA CirqueDeSQLeil
_______________________________________________
I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
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Sherwin Anderson SSCrazy Points: 2884 More actions · Answer 7

Good question, luckily read the question twice before answering.

Aaron N. Cutshall SSCrazy Eights Points: 8904 More actions · Answer 8

Bugger! I hate it when I know the right answer but click on the wrong choice! :angry:

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Revenant SSC-Forever Points: 42467 More actions · Answer 9

Revenant

SSC-Forever

Points: 42467

October 10, 2011 at 9:13 am

#1392464

Simple but neat -- thank you!

Ken SSCoach Points: 17069 More actions · Answer 10

Nice question about something that comes up regularly for me. Especially in writing queries for reporting.

James_B SSCrazy Points: 2163 More actions · Answer 11

Great question - unfortunately I got it wrong.

I thought it was too simple so I over compensated and assumed that the code would have "set ansi_nulls off" for the session since it is effectively saying "where col1 = null" rather than "where col1 is null".

OzYbOi d(-_-)b SSCarpal Tunnel Points: 4054 More actions · Answer 12

OzYbOi d(-_-)b

SSCarpal Tunnel

Points: 4054

October 10, 2011 at 10:35 am

#1392512

good question - tks

john.moreno Default port Points: 1485 More actions · Answer 13

I'd like to suggest a modification of the answer. What is happening is that the "CASE COLUMN WHEN" syntax does an equity comparision and then uses the result of that comparision, which of course fails with NULL, while the "CASE WHEN x" syntax uses the result of x. Which is why the given query returns null.

So, something like:

The CASE's statement has two alternative syntaxs, "CASE ColumnName WHEN Value" does an equity comparision between the column and the given value. This fails with NULLS unless ANSI_NULLS is off. The other syntax is "CASE WHEN EXPRESSION", which evalutes an expression (which may use any available columns) and uses the result of that expression to determine whether the condition has been met and the associated THEN used.

Evil Kraig F SSC Guru Points: 100851 More actions · Answer 14

Thanks for the question. It was a good caffination check this morning. 🙂

- Craig Farrell

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Rob Schripsema SSCertifiable Points: 7469 More actions · Answer 15

Excellent question. Thanks!

Rob Schripsema
Propack, Inc.