Calling Scalar-valued Functions in SQL

That syntax works fine for me:

CREATE FUNCTION dbo.test_func
(@in varchar(20))
RETURNS INT
AS
BEGIN
    RETURN 1
END
GO

SELECT dbo.test_func('blah')

Are you sure that the function exists as a function and under the dbo schema?

Are you sure it's not a Table-Valued Function?

The reason I ask:

CREATE FUNCTION dbo.chk_mgr(@mgr VARCHAR(50)) 
RETURNS @mgr_table TABLE (mgr_name VARCHAR(50))
AS
BEGIN 
  INSERT @mgr_table (mgr_name) VALUES ('pointy haired boss') 
  RETURN
END 
GO

SELECT dbo.chk_mgr('asdf')
GO

Result:

Msg 4121, Level 16, State 1, Line 1
Cannot find either column "dbo" or the user-defined function 
or aggregate "dbo.chk_mgr", or the name is ambiguous.

However...

SELECT * FROM dbo.chk_mgr('asdf') 

mgr_name
------------------
pointy haired boss

You are using an inline table value function. Therefore you must use Select * From function. If you want to use select function() you must use a scalar function.

https://msdn.microsoft.com/fr-fr/library/ms186755%28v=sql.120%29.aspx

Can do the following

PRINT dbo.[FunctionName] ( [Parameter/Argument] )

E.g.:

PRINT dbo.StringSplit('77,54')