SQL Server - Altering tables and renaming columns

 A quick post on how to alter the data types and nullable attributes for a table.

In addition, since you would think that the same command statement would also take care of renaming a column I've added that as well.

First we create a test table to work with, as usual I'll stick with cars.

 After the table has been created, we realized that the Make is only five characters.  That will need to be fixed.

For some reason, it was decided that the Year can not be nullable.  They don't care about the Make or Model, go figure.

Then finally, we are told that Year really shouldn't be used.  They want us to use ModelYear instead.  But wait, ALTER TABLE just doesn't allow column name changes.  So we must use the system stored procedure SP_RENAME.

Below we'll be using SP_RENAME to rename the column.  But it can also be used to rename databases, indexes, objects and user data types.  See: msdn:SP_RENAME for more information.

 
-- Below creates a sample table called cars:

--- Create a Table ---
CREATE TABLE dbo.Cars
(
    ID     INT          Identity(1,1) NOT NULL
  , Year   INT         NULL
  , Make   VarChar(05) NULL
  , Model  VarChar(50) NULL
)

GO

-- the Alter TABLE statement allows you to modify the
-- data type and the nullable attribute of a column.


-- Here we are increasing the size of the Make
-- column to 50 characters from the initially created 05
ALTER TABLE dbo.Cars
    ALTER COLUMN Make Varchar(50) NULL
   
 
GO    

-- Let's prevent null values from being entered
-- into the Year column. 
--Note: If there are already null values in the
--Year column, this command would fail.
ALTER TABLE dbo.Cars
    ALTER COLUMN Year INT NOT NULL

GO

-- There is no ALTER command to rename a column
-- for this you will need to use 'sp_rename'
EXEC sp_rename 'dbo.Cars.Year', 'ModelYear', 'column'


--Note: You will receive a caution message indicating that
--      your change could break any existing scripts or
--      stored procedures.  So make sure you update any
--      affected stored procedures or scripts.