Should I use And or OR in the Where Clause?

Question

2 Databases have been merged, and in the purge some data was omitted, so I am running clean-up.  Now I need a query to show me if item1 is null, then check olditem1 if both fields are null then ignore the record completely.  But If either field
has a value I need it returned.  So 1st check item1 if that field is not null, then return the record, if item1 is null, check olditem1 if that field is not null then return the record.  If both fileds are null, ignore the record and let's check
the next one.
Sample Data;
Select
Test.StaffIDID,
Test.purchasedfrom,
Test.date,
case when Test.item1 is null then Test.olditem1 else null end as [1st Item],
case when Test.item2 is null then Test.olditem2 else null end as [2nd Item],
From internetsales Test
CREATE TABLE Test
StaffID INT NOT NULL PRIMARY KEY,
purchasedfrom NVARCHAR(30) NOT NULL,
date DateTime NOT NULL,
item1 NVARCHAR(50),
item2 NVARCHAR(50),
olditem1 NVARCHAR(50),
olditem2 NVARCHAR(50)
INSERT Test VALUES
(2, 'web1', '2010-01-02', 'stereo', 'NULL', 'NULL', 'NULL'),
(3, 'web3', '2011-02-15', 'NULL', 'microphone', 'NULL', 'NULL'),
(4, 'web14', '2014-02-21', 'NULL', 'NULL', 'NULL', 'headset'),
(5, 'web81', '2015-01-01', 'NULL', 'NULL', 'MP3 Player', 'NULL');
(6, 'web18', '2011-01-01', 'Dryer', 'NULL', 'MP3 Player', 'NULL');
(7, 'web8', '2009-01-01', 'NULL', 'NULL', 'Stove', ''NULL);
(8, 'web828', '2002-01-01', 'NULL', 'NULL', 'NULL', 'USB HUB');
(9, 'web88', '2007-01-01', 'Refrigerator', 'NULL', 'NULL', 'NULL');
(10, 'web89', '2009-01-01', 'NULL', 'NULL', 'NULL', 'NULL');
Desired returned result sets would be StaffIDs: 2,5,6,7,9 -- as they have a value for item1 or olditem1

Answer 1

Looks like you totally ignored my answer :-(
well... you have your reason probably...
You do realize that I gave you the answer from the start?!?
Hi,
your sample data do not include any NULL value. Blank string is not NULL.
Please clarify your question and give us the result that you want to get, according to your sample data.
* if your data is NULL and not empty string that you can use COALESCE(item1, olditem1,'') in order to get the first value that is not NULL. if both
NULL then it will return blank string as this is the first value that is not null
  Ronen Ariely
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Using nested IIF can be done directly with the
COALESCE function.
The execution plan is the same, but the code is much cleaner and easier to write or read.
There is a reason for this function.
* In your current needs there are only 2 nested IIF, but you should know about COALESCE function! Once you get more complex situation you will be able to get a solution much faster and probably without any mistake on the first try.
try to use 5 nested IIF... using COALESCE  this is simple as 2 or 10... all you need is to write all the values and the function will return the first that is not NULL
Any way, I hope this is useful for people that will come to this thread in future :-)
-- SOLUTION 1: using nested IIF
SELECT StaffID, purchasedfrom, date,
IIF(ITEM1 IS NOT NULL, ITEM1, IIF(OLDITEM1 IS NOT NULL, OLDITEM1,NULL)) AS [1ST ITEM],
IIF(ITEM2 IS NOT NULL, ITEM2,IIF(OLDITEM2 IS NOT NULL, OLDITEM2,NULL)) AS [2ND ITEM]
FROM Test
-- solution 2: using COALESCE
SELECT
StaffID, purchasedfrom, date,
COALESCE(ITEM1, OLDITEM1) AS [1ST ITEM],
COALESCE(ITEM2, OLDITEM2) AS [2ND ITEM]
FROM Test
-- Whish solution look simpler to read, write or use?
-- The execution plan is the same, but it is always good idea to make sure if you are not sure :-)
I hope this is useful :-)
  Ronen Ariely
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