RENAME COLUMN/ ADD COLUMN

IF NOT EXISTS (SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'DOCUMENT' AND COLUMN_NAME = 'DOCUMENTDUEDATE')
BEGIN
ALTER TABLE DOCUMENT ADD DOCUMENTDUEDATE DATETIME
END

--To rename an existing column
--EXEC sp_rename 'DOCUMENT.DUEDATE','DOCUMENTDUEDATE','COLUMN'