Sql-server – How to test for the existence of a user in SQL Server

sql-serversql-server-2005sql-server-2008sql-server-2012

I'd like to drop a user in a SQL Server script but I'll need to test for existence first or I'll get script errors. When dropping tables or stored procs, I check the sysobjects table like so:

IF EXISTS (
    SELECT * 
    FROM   sysobjects 
    WHERE  id = object_id(N'[dbo].[up_SetMedOptions]') 
    AND    OBJECTPROPERTY(id, N'IsProcedure') = 1
)
Drop Procedure up_SetMedOptions;
GO

What is the corollary for checking for a user? Note that I am NOT asking about a database login to the server! The question pertains to a User in a specific database.

Best Solution

SSMS scripts it in the following way:

For SQL 2005/2008:

IF  EXISTS (SELECT * FROM sys.database_principals WHERE name = N'username')
DROP USER [username]

For SQL 2000:

IF  EXISTS (SELECT * FROM dbo.sysusers WHERE name = N'username')
EXEC dbo.sp_revokedbaccess N'username'

Syntax:

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES

Example:

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.

Notes:

Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.

Sql – How to return only the Date from a SQL Server DateTime datatype

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @your_date))

for example

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, GETDATE()))

gives me

2008-09-22 00:00:00.000

Pros:

No varchar<->datetime conversions required
No need to think about locale

Best Solution

Related Solutions

Sql – Add a column with a default value to an existing table in SQL Server

Syntax:

Example:

Notes:

Sql – How to return only the Date from a SQL Server DateTime datatype

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