T-SQL: converting NULL values into empty string

Hi, I'd like to have empty  string values in the query results instead of NULL. What is the best way to accomplish this for multiple datatypes including datetime, numeric, int, varchar?

Thank you in advance.
quasar_eeAsked:
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Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
COALESCE will return the first non-NULL value it finds, so...

Declare @foo varchar(10) = NULL
SELECT COALESCE(@foo, '')

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nemws1Database AdministratorCommented:
As Jimhorn says, COALESCE(), which is an excellent choice.

The other option is to use ISNULL(), for a single comparison.

Declare @foo varchar(10) = NULL;
SELECT ISNULL(@foo, '');

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COALESCE() lets you do this:

Declare @foo varchar(10) = NULL;
Declare @bar varchar(10) = NULL;
Declare @baz varchar(10) = NULL;
SELECT COALESCE(@foo, @bar, @baz, '');

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awking00Commented:
Coalesce is the way I'd go as well but I'm not sure you can insert an empty string into a datetime and/or numeric field.
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lcohanDatabase AnalystCommented:
If the table column(s) allow NULLs then you can if not....you can-not.
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PortletPaulfreelancerCommented:
I believe the point made by awking00 is that you can't insert an "empty string" into a non-string column.

Try this:
declare @d as datetime
declare @n as numeric
declare @i as int
declare @v as varchar

select
        cast(null as datetime) as dt_col
      , cast(null as numeric ) as nu_col
      , cast(null as int     ) as in_col
      , cast(null as varchar ) as va_col

union all

select
        isnull(@d, '')
      , isnull(@n, '')
      , isnull(@i, '')
      , isnull(@v, '')

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All columns would have to be string types to accept ''

btw: whilst coalesce is v.cool I see no particular advantage in using it unless you have more than one expression to evaluate. As coalesce allows a variable number of parameters it's my view there is slightly more overhead to assess the number of parameters supplied. ISNULL would be my suggestion. But both will do the job.
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Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
Five good expert comments.  I think we've nailed this one.

quasar_ee - How's it goin', eh?
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