All time show NULL value please help me...

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All Time Show Null value
Please help me what is the wrong in my code

What I have tried:

declare @mxdbvlu  int
 declare @dbvlunm int
  set @mxdbvlu= (select max(Database_name) from TBL_FY_SELECT_1)
 if @mxdbvlu = null 
 set @dbvlunm=1000
 else 
 set @dbvlunm=sum(@mxdbvlu+1)
  select @dbvlunm,@mxdbvlu

Posted 8-Feb-19 17:06pm

Jayanta Modak

Updated 12-Feb-19 6:41am

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OriginalGriff · Answer 1 · 2019-02-08T19:55:00

If I create a table with two columns: ID (int, Identity) and Database_name (NVARCHAR, MAX) and run your code, I do indeed get NULL, NULL.

But add two data rows:

SQL

ID      Database_name
1       AAAA      
2       AAAB

And I don't - I get an exception becuase it can't convert "AAAA" to an integer value.
If I replace the data with this:

SQL

ID      Database_name
1       1111      
2       1112

Then I get "reasonable" data:

(No column name) (No column name)
1113             1112

So your choice of column name is clearly wrong: you can't put a name in there.

And I can only replicate your failure when there are no rows - so start by checking your data.

But ... if you are using this to build a new database with sequential names each time you add some data, then that's probably a bad design. I'd strongly suggest that you rethink exactly why you decided this would be a good solution - both from a "why didn't I use an IDENTITY column?" POV, and a "why the heck do I need new databases at all, that's just silly" approach.

Richard Deeming · Answer 2 · 2019-02-12T06:41:00

I can see two obvious issues with your code:

SQL

if @mxdbvlu = null

If either or both operands are NULL, the comparison operators (=, !=) will return UNKNOWN. This is neither true nor false, so the If branch will not be executed.

To test whether a value is NULL, use Is Null instead:
IS NULL (Transact-SQL) - SQL Server | Microsoft Docs[^]
SQL and the Snare of Three-Valued Logic - Simple Talk[^]

SQL

set @dbvlunm=sum(@mxdbvlu+1)

Since you're not calculating an aggregate over a set of records, you don't need Sum(...) here. Just use:

SQL

set @dbvlunm = @mxdbvlu + 1

All time show NULL value please help me...

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