Change a Nullable column to NOT NULL with Default Value

Question

I came across an old table today with a datetime column called \'Created\' which allows nulls. Now, I\'d want to change this so that it is NOT NULL, and also include a constrai

Answer 1

you need to execute two queries:

One - to add the default value to the column required

ALTER TABLE 'Table_Name` ADD DEFAULT 'value' FOR 'Column_Name'

i want add default value to Column IsDeleted as below:

Example: ALTER TABLE [dbo].[Employees] ADD Default 0 for IsDeleted

Two - to alter the column value nullable to not null

ALTER TABLE 'table_name' ALTER COLUMN 'column_name' 'data_type' NOT NULL

i want to make the column IsDeleted as not null

ALTER TABLE [dbo].[Employees] Alter Column IsDeleted BIT NOT NULL

Answer 2

I think you will need to do this as three separate statements. I've been looking around and everything i've seen seems to suggest you can do it if you are adding a column, but not if you are altering one.

ALTER TABLE dbo.MyTable
ADD CONSTRAINT my_Con DEFAULT GETDATE() for created

UPDATE MyTable SET Created = GetDate() where Created IS NULL

ALTER TABLE dbo.MyTable 
ALTER COLUMN Created DATETIME NOT NULL 

Answer 3

You may have to first update all the records that are null to the default value then use the alter table statement.

Update dbo.TableName
Set
Created="01/01/2000"
where Created is NULL

Answer 4

If its SQL Server you can do it on the column properties within design view

Try this?:

ALTER TABLE dbo.TableName 
  ADD CONSTRAINT DF_TableName_ColumnName
    DEFAULT '01/01/2000' FOR ColumnName

Answer 5

Try this

ALTER TABLE table_name ALTER COLUMN col_name data_type NOT NULL;