how to ignore null columns

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how to ignore null columns

josetur12

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Points: 1424
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February 27, 2013 at 1:06 pm

#274581

Hi, I need help again.
I have a table with five approval dates. The columns could have a value but some could only have one, two or three. Out of all the columns, I need to get the last approval date.
For example, in my sample data, I need to retrieve timestamp4 in row 1, timestamp3 in row 2 and 3, and timestamp2 in row 4.
DDL and sample data.
CREATE TABLE [Dates](
ID [int] NULL,
PO [varchar](50) NULL,
timestamp1 [datetime] NULL,
timestamp2 [datetime] NULL,
timestamp3 [datetime] NULL,
timestamp4 [datetime] NULL
)
Insert into [Dates]
([ID], [PO], timestamp1, timestamp2, timestamp3, timestamp4)
SELECT 1, '12345', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM' UNION ALL
SELECT 1, '12345', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM', null UNION ALL
SELECT 1, '12345', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM', null UNION ALL
SELECT 1, '12345', 'Jul 3 2012 4:48PM', 'Jul 3 2012 4:48PM', null, null
Thanks.

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Lowell SSC Guru Points: 323518 More actions · Answer 1

great job on giving us the setup DDL and Data.

Your data has all the same datetimes, so it'll probably look better when you compare the example with real data.

this seems to work for me, is this what you are after?

SELECT

ID,

PO,

CASE WHEN ISNULL(timestamp1,'1900-01-01') >= ISNULL(timestamp2,'1900-01-01')

AND ISNULL(timestamp1,'1900-01-01') >= ISNULL(timestamp3,'1900-01-01')

AND ISNULL(timestamp1,'1900-01-01') >= ISNULL(timestamp4,'1900-01-01')

THEN ISNULL(timestamp1,'1900-01-01')

WHEN ISNULL(timestamp2,'1900-01-01') >= ISNULL(timestamp1,'1900-01-01')

AND ISNULL(timestamp2,'1900-01-01') >= ISNULL(timestamp3,'1900-01-01')

AND ISNULL(timestamp2,'1900-01-01') >= ISNULL(timestamp4,'1900-01-01')

THEN ISNULL(timestamp2,'1900-01-01')

WHEN ISNULL(timestamp3,'1900-01-01') >= ISNULL(timestamp1,'1900-01-01')

AND ISNULL(timestamp3,'1900-01-01') >= ISNULL(timestamp2,'1900-01-01')

AND ISNULL(timestamp3,'1900-01-01') >= ISNULL(timestamp4,'1900-01-01')

THEN ISNULL(timestamp3,'1900-01-01')

WHEN ISNULL(timestamp4,'1900-01-01') >= ISNULL(timestamp1,'1900-01-01')

AND ISNULL(timestamp4,'1900-01-01') >= ISNULL(timestamp2,'1900-01-01')

AND ISNULL(timestamp4,'1900-01-01') >= ISNULL(timestamp3,'1900-01-01')

THEN ISNULL(timestamp4,'1900-01-01')

END As MaxDate

FROM [Dates]

Lowell

--help us help you! If you post a question, make sure you include a CREATE TABLE... statement and INSERT INTO... statement into that table to give the volunteers here representative data. with your description of the problem, we can provide a tested, verifiable solution to your question! asking the question the right way gets you a tested answer the fastest way possible!

Lowell SSC Guru Points: 323518 More actions · Answer 2

or did you mean the last non-null column, regardless of the datetime value? my example above finds the highest date, regardless of which column.

in that case, assuming your app files the columns up in left to right order(timestamp1,imestamp2,imestamp3,imestamp4) it would be like this:

SELECT

ID,

PO,

COALESCE(timestamp4,timestamp3,timestamp2,timestamp1) AS MaxDate

FROM [Dates]

Lowell

--help us help you! If you post a question, make sure you include a CREATE TABLE... statement and INSERT INTO... statement into that table to give the volunteers here representative data. with your description of the problem, we can provide a tested, verifiable solution to your question! asking the question the right way gets you a tested answer the fastest way possible!

josetur12 Default port Points: 1424 More actions · Answer 3

I need to get the last value regardless of the actual date.

I tried both solutions and both work.

Thank you.

Jeff Moden SSC Guru Points: 1004356 More actions · Answer 4

josetur12 (2/27/2013)
I need to get the last value regardless of the actual date.
I tried both solutions and both work.
Thank you.

You might also want to consider changing the structure of the table. The way it is, it'll be interesting when they come up with a 5th date.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

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