How to check existence of a sql server object and drop it?

Question

EDIT: the function creation was missing, sorry about that

I have a T-SQL request that goes:

DECLARE @IsSomething bit
SET @IsSomething = 0
IF /some tests/ SET @IsSomething = 1
EXEC('
CREATE FUNCTION IsSomething ()
RETURNS bit
AS
BEGIN
    RETURN ' + @IsSomething + '
END')

Of course if I run it twice I get

There is already an object named 'IsSomething ' in the database. 

How would I do something like this:

IF EXIST @IsSomething DESTROY @IsSomething // (Pseudo bad code)

Solution 1

IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id (N'[dbo].[IsSomething]') AND OBJECTPROPERTY(id, N'IsFunction') = 1) 

DROP function IsSomething
GO

Solution 2

The answer to your edited question is:

if object_id('IsSomething', 'fn') is not null drop function IsSomething
go

Solution 3

The template, from Visual Studio 2008 Add -> Stored Procedure Script is

IF EXISTS (SELECT * FROM sysobjects WHERE type = 'P' AND name = 'Stored_Procedure_Name')
    BEGIN
        DROP  Procedure  Stored_Procedure_Name
    END

GO

CREATE Procedure Stored_Procedure_Name
/*
    (
        @parameter1 int = 5,
        @parameter2 datatype OUTPUT
    )

*/
AS


GO

/*
GRANT EXEC ON Stored_Procedure_Name TO PUBLIC

GO
*/

For a Procedure, Sql Server Management Studio gives the following script to drop

IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[usp_DeleteXyz]') AND type in (N'P', N'PC'))
DROP PROCEDURE [dbo].[usp_DeleteXyz]

likewise for a Function it's generated script is

IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[udf_GetXyz]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[udf_GetXyz]

I've mostly seen the latter forms (2-line versions) in most codebases I've worked on, and there's no need to declare a variable.

Solution 4

For SQL Server 2016 and newer you can do the following:

DROP DATABASE IF EXISTS [DBName]

ALTER TABLE [TABLENAME] DROP COLUMN IF EXISTS [COLUMNNAME]

Solution 5

Seems analogous to any other language where you try to declare the same global variable multiple times. Normally we don't write:

var a;
a = 0;
...
...
undefine a;
a = 1;
...
...
undefine a;
a = 2;

Seems to me like you just need to be aware of the structure of the code you are writing.

I wouldn't consider a declared variable to be a "database object", BTW. But your question makes more sense if for some reason you do.

View more solutions

Comments

[dkretz]

A "define" statement has a specific limited scope. A defined variable shouldn't outlive the execution of a single script, nor interact with other scripts unless called as subscripts.

[marcgg]

the drop part is not working. If my variable is declared like this: DECLARE @IsSomething bit, how should I drop it?

[marcgg]

Ok I get it thanks to Ben M. Sorry my question was confusing :\ It's updated now with the real problem.

[Chris McCall]

edited to reflect reality. Note that I didn't use the IF OBJECT_ID('YourObject', 'ObjectsType') IS NOT NULL style because it's too sloppy and would drop other object types you may not have intended.

[Ben M]

How's that, Chris? (In my answer, for example.)

[João Paladini]

Yes. Because A) "<ObjectsType>" has to be replaced with the objects type name, ie., "DROP TABLE [..]" or "DROP INDEX [..], and B) "bit" is not an Object Type, it is a domain type and you cannot drop them.

[João Paladini]

Ah, I see now, you've changed your question so that it is clear that you are trying to DROP a variable. You can't do that, you have to start another session/batch. (In scripts, GO will do this)

[marcgg]

from Robert Paulson's answer I'd say that Chris is right about his answer being the best one, but I'm not sure.

[Ben M]

Either one works--I'm not sure what Chris means about other object types being dropped, since you can't DROP FUNCTION a table, for example.

[Chris McCall]

In the effort to construct a reply, I've discovered I have no idea what the Hell I meant by that.

[Chris McCall]

Yeah, that looks fine, I think we're all slugging it out for that last 1% of correctedness

[dkretz]

The problem is that you IsSomething (the function) and @IsSomething (the variable) are two distinct things with no relationship to each other.