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

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.

ALTER TABLE Protocols
ADD ProtocolTypeID int NOT NULL DEFAULT(1)
GO

The inclusion of the DEFAULT fills the column in existing rows with the default value, so the NOT NULL constraint is not violated.

When adding a nullable column, WITH VALUES will ensure that the specific DEFAULT value is applied to existing rows:

ALTER TABLE table
ADD column BIT     -- Demonstration with NULL-able column added
CONSTRAINT Constraint_name DEFAULT 0 WITH VALUES

ALTER TABLE <table name> 
ADD <new column name> <data type> NOT NULL
GO
ALTER TABLE <table name> 
ADD CONSTRAINT <constraint name> DEFAULT <default value> FOR <new column name>
GO

ALTER TABLE MYTABLE ADD MYNEWCOLUMN VARCHAR(200) DEFAULT 'SNUGGLES'

The most basic version with two lines only

ALTER TABLE MyTable
ADD MyNewColumn INT NOT NULL DEFAULT 0

Beware when the column you are adding has a NOT NULL constraint, yet does not have a DEFAULT constraint (value). The ALTER TABLE statement will fail in that case if the table has any rows in it. The solution is to either remove the NOT NULL constraint from the new column, or provide a DEFAULT constraint for it.

Use:

-- Add a column with a default DateTime  
-- to capture when each record is added.

ALTER TABLE myTableName  
ADD RecordAddedDate SMALLDATETIME NULL DEFAULT (GETDATE())  
GO 

If you want to add multiple columns you can do it this way for example:

ALTER TABLE YourTable
    ADD Column1 INT NOT NULL DEFAULT 0,
        Column2 INT NOT NULL DEFAULT 1,
        Column3 VARCHAR(50) DEFAULT 'Hello'
GO

To add a column to an existing database table with a default value, we can use:

ALTER TABLE [dbo.table_name]
    ADD [Column_Name] BIT NOT NULL
Default ( 0 )

Here is another way to add a column to an existing database table with a default value.

A much more thorough SQL script to add a column with a default value is below including checking if the column exists before adding it also checkin the constraint and dropping it if there is one. This script also names the constraint so we can have a nice naming convention (I like DF_) and if not SQL will give us a constraint with a name which has a randomly generated number; so it's nice to be able to name the constraint too.

-------------------------------------------------------------------------
-- Drop COLUMN
-- Name of Column: Column_EmployeeName
-- Name of Table: table_Emplyee
--------------------------------------------------------------------------
IF EXISTS (
            SELECT 1
            FROM INFORMATION_SCHEMA.COLUMNS
            WHERE TABLE_NAME = 'table_Emplyee'
              AND COLUMN_NAME = 'Column_EmployeeName'
           )
    BEGIN

        IF EXISTS ( SELECT 1
                    FROM sys.default_constraints
                    WHERE object_id = OBJECT_ID('[dbo].[DF_table_Emplyee_Column_EmployeeName]')
                      AND parent_object_id = OBJECT_ID('[dbo].[table_Emplyee]')
                  )
            BEGIN
                ------  DROP Contraint

                ALTER TABLE [dbo].[table_Emplyee] DROP CONSTRAINT [DF_table_Emplyee_Column_EmployeeName]
            PRINT '[DF_table_Emplyee_Column_EmployeeName] was dropped'
            END
     --    -----   DROP Column   -----------------------------------------------------------------
        ALTER TABLE [dbo].table_Emplyee
            DROP COLUMN Column_EmployeeName
        PRINT 'Column Column_EmployeeName in images table was dropped'
    END

--------------------------------------------------------------------------
-- ADD  COLUMN Column_EmployeeName IN table_Emplyee table
--------------------------------------------------------------------------
IF NOT EXISTS (
                SELECT 1
                FROM INFORMATION_SCHEMA.COLUMNS
                WHERE TABLE_NAME = 'table_Emplyee'
                  AND COLUMN_NAME = 'Column_EmployeeName'
               )
    BEGIN
    ----- ADD Column & Contraint
        ALTER TABLE dbo.table_Emplyee
            ADD Column_EmployeeName BIT   NOT NULL
            CONSTRAINT [DF_table_Emplyee_Column_EmployeeName]  DEFAULT (0)
        PRINT 'Column [DF_table_Emplyee_Column_EmployeeName] in table_Emplyee table was Added'
        PRINT 'Contraint [DF_table_Emplyee_Column_EmployeeName] was Added'
     END

GO

These are two ways to add a column to an existing database table with a default value.

Use:

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

Reference: ALTER TABLE (Transact-SQL) (MSDN)

You can do the thing with T-SQL in the following way.

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

As well as you can use SQL Server Management Studio also by right clicking table in the Design menu, setting the default value to table.

And furthermore, if you want to add the same column (if it does not exists) to all tables in database, then use:

 USE AdventureWorks;
 EXEC sp_msforeachtable
'PRINT ''ALTER TABLE ? ADD Date_Created DATETIME DEFAULT GETDATE();''' ;

In SQL Server 2008-R2, I go to the design mode - in a test database - and add my two columns using the designer and made the settings with the GUI, and then the infamous Right-Click gives the option "Generate Change Script"!

Bang up pops a little window with, you guessed it, the properly formatted guaranteed-to-work change script. Hit the easy button.

Alternatively, you can add a default without having to explicitly name the constraint:

ALTER TABLE [schema].[tablename] ADD  DEFAULT ((0)) FOR [columnname]

If you have an issue with existing default constraints when creating this constraint then they can be removed by:

alter table [schema].[tablename] drop constraint [constraintname]

This can be done in the SSMS GUI as well. I show a default date below but the default value can be whatever, of course.

Put your table in design view (Right click on the table in object explorer->Design) Add a column to the table (or click on the column you want to update if it already exists) In Column Properties below, enter (getdate()) or 'abc' or 0 or whatever value you want in Default Value or Binding field as pictured below:

https://i.stack.imgur.com/FQbi1.png

ALTER TABLE ADD ColumnName {Column_Type} Constraint

The MSDN article ALTER TABLE (Transact-SQL) has all of the alter table syntax.

Example:

ALTER TABLE [Employees] ADD Seniority int not null default 0 GO

Example:

ALTER TABLE tes 
ADD ssd  NUMBER   DEFAULT '0';

First create a table with name student:

CREATE TABLE STUDENT (STUDENT_ID INT NOT NULL)

Add one column to it:

ALTER TABLE STUDENT 
ADD STUDENT_NAME INT NOT NULL DEFAULT(0)

SELECT * 
FROM STUDENT

The table is created and a column is added to an existing table with a default value.

https://i.stack.imgur.com/lMXvg.png

This has a lot of answers, but I feel the need to add this extended method. This seems a lot longer, but it is extremely useful if you're adding a NOT NULL field to a table with millions of rows in an active database.

ALTER TABLE {schemaName}.{tableName}
    ADD {columnName} {datatype} NULL
    CONSTRAINT {constraintName} DEFAULT {DefaultValue}

UPDATE {schemaName}.{tableName}
    SET {columnName} = {DefaultValue}
    WHERE {columName} IS NULL

ALTER TABLE {schemaName}.{tableName}
    ALTER COLUMN {columnName} {datatype} NOT NULL

What this will do is add the column as a nullable field and with the default value, update all fields to the default value (or you can assign more meaningful values), and finally it will change the column to be NOT NULL.

The reason for this is if you update a large scale table and add a new not null field it has to write to every single row and hereby will lock out the entire table as it adds the column and then writes all the values.

This method will add the nullable column which operates a lot faster by itself, then fills the data before setting the not null status.

I've found that doing the entire thing in one statement will lock out one of our more active tables for 4-8 minutes and quite often I have killed the process. This method each part usually takes only a few seconds and causes minimal locking.

Additionally, if you have a table in the area of billions of rows it may be worth batching the update like so:

WHILE 1=1
BEGIN
    UPDATE TOP (1000000) {schemaName}.{tableName}
        SET {columnName} = {DefaultValue}
        WHERE {columName} IS NULL

    IF @@ROWCOUNT < 1000000
        BREAK;
END

Try this

ALTER TABLE Product
ADD ProductID INT NOT NULL DEFAULT(1)
GO

SQL Server + Alter Table + Add Column + Default Value uniqueidentifier

ALTER TABLE Product 
ADD ReferenceID uniqueidentifier not null 
default (cast(cast(0 as binary) as uniqueidentifier))

IF NOT EXISTS (
    SELECT * FROM INFORMATION_SCHEMA.COLUMNS
    WHERE TABLE_NAME ='TABLENAME' AND COLUMN_NAME = 'COLUMNNAME'
)
BEGIN
    ALTER TABLE TABLENAME ADD COLUMNNAME Nvarchar(MAX) Not Null default
END

--Adding Value with Default Value
ALTER TABLE TestTable
ADD ThirdCol INT NOT NULL DEFAULT(0)
GO

This is for SQL Server:

ALTER TABLE TableName
ADD ColumnName (type) -- NULL OR NOT NULL
DEFAULT (default value)
WITH VALUES

Example:

ALTER TABLE Activities
ADD status int NOT NULL DEFAULT (0)
WITH VALUES

If you want to add constraints then:

ALTER TABLE Table_1
ADD row3 int NOT NULL
CONSTRAINT CONSTRAINT_NAME DEFAULT (0)
WITH VALUES

Add a new column to a table:

ALTER TABLE [table]
ADD Column1 Datatype

For example,

ALTER TABLE [test]
ADD ID Int

If the user wants to make it auto incremented then:

ALTER TABLE [test]
ADD ID Int IDENTITY(1,1) NOT NULL

This can be done by the below code.

CREATE TABLE TestTable
    (FirstCol INT NOT NULL)
    GO
    ------------------------------
    -- Option 1
    ------------------------------
    -- Adding New Column
    ALTER TABLE TestTable
    ADD SecondCol INT
    GO
    -- Updating it with Default
    UPDATE TestTable
    SET SecondCol = 0
    GO
    -- Alter
    ALTER TABLE TestTable
    ALTER COLUMN SecondCol INT NOT NULL
    GO

Try with the below query:

ALTER TABLE MyTable
ADD MyNewColumn DataType DEFAULT DefaultValue

This will add a new column into the Table.

ALTER TABLE tbl_table ADD int_column int NOT NULL DEFAULT(0)

From this query you can add a column of datatype integer with default value 0.

Well, I now have some modification to my previous answer. I have noticed that none of the answers mentioned IF NOT EXISTS. So I am going to provide a new solution of it as I have faced some problems altering the table.

IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.columns WHERE table_name = 'TaskSheet' AND column_name = 'IsBilledToClient')
BEGIN
ALTER TABLE dbo.TaskSheet ADD
 IsBilledToClient bit NOT NULL DEFAULT ((1))
END
GO

Here TaskSheet is the particular table name and IsBilledToClient is the new column which you are going to insert and 1 the default value. That means in the new column what will be the value of the existing rows, therefore one will be set automatically there. However, you can change as you wish with the respect of the column type like I have used BIT, so I put in default value 1.

I suggest the above system, because I have faced a problem. So what is the problem? The problem is, if the IsBilledToClient column does exists in the table table then if you execute only the portion of the code given below you will see an error in the SQL server Query builder. But if it does not exist then for the first time there will be no error when executing.

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