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Home » SQL Server 7,2000 » T-SQL » how to ignore null columns
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josetur12
Posted Wednesday, February 27, 2013 1:06 PM
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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.
Post #1424720
Lowell
Posted Wednesday, February 27, 2013 1:19 PM


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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

--There is no spoon, and there's no default ORDER BY in sql server either.
Actually, Common Sense is so rare, it should be considered a Superpower. --my son
Post #1424723
Lowell
Posted Wednesday, February 27, 2013 1:23 PM


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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

--There is no spoon, and there's no default ORDER BY in sql server either.
Actually, Common Sense is so rare, it should be considered a Superpower. --my son
Post #1424726
josetur12
Posted Wednesday, February 27, 2013 1:41 PM
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I need to get the last value regardless of the actual date.

I tried both solutions and both work.
Thank you.
Post #1424732
Jeff Moden
Posted Wednesday, February 27, 2013 10:19 PM


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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."

For better, quicker answers on T-SQL questions, click on the following...
http://www.sqlservercentral.com/articles/Best+Practices/61537/

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http://www.sqlservercentral.com/articles/SQLServerCentral/66909/
Post #1424898
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