Remove a column when meet a certain condition in CASE WHEN

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SQL-Server-2008R2

Hi, I have the following SQL statement in which I want to remove a certain column when a condition is met. Below are my SQL statement:

SQL

CASE @p_ReportType WHEN 1 THEN NULL WHEN ISNULL(@p_ReportType, 0) THEN row_number() OVER (ORDER BY  EventId desc)+1 END AS MeasurementGroupId

For the above scenario, when the @p_ReportType is 1 then the MeasurementGroupId is removed else the MeasurementGroupId is remained. Any helps are appreciated.

Posted 8-Mar-15 16:29pm

Jamie888

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_Maxxx_ 8-Mar-15 22:34pm

When you say you want the column removed, do you mean not included in the results at all, or returned as Null?
If you want to not include the column, then you will have to resort to dynamic SQL - i.e. build up the sql string and execute it.
If you are happy to return null, then
Select Case When @p_reportType = 1 Then Null Else row_number() END as MeasurementGroupId

Jamie888 8-Mar-15 22:39pm

I have tried execute it using different ways. First would be only one condition whereas it returns the result I want. After that I add in the second condition whereas it returns the result I do not want. So I would prefer the MeasurementGroupId is returned as 0 when first condition is met.

ZurdoDev 9-Mar-15 8:39am

Where exactly are you stuck? This question does not make sense.

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Maciej Los · Answer 1 · 2015-03-09T21:34:00

Solution 1

Above code does not remove any column! It "evaluates a list of conditions and returns one of multiple possible result expressions".

See:
CASE (sql)[^]

Posted 9-Mar-15 21:34pm

Maciej Los