Is there any difference between a NULL and a Blank field in MS SQL

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Is there any difference between a NULL and a Blank field in MS SQL

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shameersinbox

Posted Tuesday, October 14, 2008 4:20 AM

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My question is, is there any difference between a NULL and a Blank
field in MS SQL or are they the same?
I have faced some problems while retrieving the records from the database.How to overcome......
Any one help
Thanks
Shameer

Post #585323

vyas

Posted Tuesday, October 14, 2008 4:36 AM

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Both are different.Null is value which is unknown.

If you want to extract the null values use is null

If you want to extract blank values use = ' '

Post #585333

rajasekhar.bollareddy

Posted Friday, February 25, 2011 3:30 AM

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insert into employee(emp_no,emp_fname,emp_lname,dept_no) values(29346,null,'james','d2')
10102 ann jones d3
18316 john barrimore d1
25348 matthew smith d3
29346 james james d2
29347 NULL james d2

insert into employee(emp_no,emp_lname,dept_no) values(29346,'james','d2')
10102 ann jones d3
18316 john barrimore d1
25348 matthew smith d3
29346 james james d2
29347 NULL james d2

so no difference both are same

Post #1069487

Carlton Leach

Posted Friday, February 25, 2011 4:43 AM

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rajasekhar.bollareddy (2/25/2011)

so no difference both are same

An empty string an NULL are the same? Nope.

As stated NULL is an unknown value not an empty string (we know it's a string, we know it's empty).

If your having trouble retrieving things from a column that could be either use ISNULL (look in books online). Use with caution as this can be a performance nightmare.

Carlton.

Post #1069509

ALZDBA

Posted Friday, February 25, 2011 5:24 AM

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If to you NULL = '' then declare you column NOT NULL !! (maybe even add "with default '' )

there are some nice article regarding NULL and its impact for mistakes .... to happen ....

-http://www.sqlservercentral.com/articles/Advanced+Querying/2829/

- http://www.sqlservercentral.com/articles/T-SQL/understandingthedifferencebetweenisnull/871/

- http://www.sqlservercentral.com/articles/ANSI_NULLs/69234/

- http://www.sqlservercentral.com/articles/Advanced+Querying/gotchasqlaggregatefunctionsandnull/1947/

- http://www.sqlservercentral.com/articles/Advanced/2921/

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     Jul 13

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