Idempotent SQL Alter Table Statements

IdempotentSQLAlterTableAddColumn.sql

IF NOT EXISTS 
(
    SELECT * FROM [information_schema].[columns] 
    WHERE   table_name = 'Customer' 
    AND table_schema = 'dbo'
    AND column_name = 'FavoriteColorId'
)
BEGIN
    ALTER TABLE [dbo].[Customer]
    ADD FavoriteColorId int
END

IdempotentSQLAlterTableRemoveColumn.sql

IF EXISTS 
(
    SELECT * FROM [information_schema].[columns] 
    WHERE   table_name = 'Customer' 
    AND table_schema = 'dbo'
    AND column_name = 'FavoriteColorId'
)
BEGIN
    ALTER TABLE [dbo].[Customer]
    DROP COLUMN FavoriteColorId
END

Thanks to Phil Haack for this...http://haacked.com/archive/2006/07/05/bulletproofsqlchangescriptsusinginformation_schemaviews.aspx