A. Alter a table to add a new column
This example adds a column that allows null values and has no values provided through a DEFAULT definition. Each row will have a NULL in the new column.
CREATE TABLE doc_exa ( column_a INT)
GO
ALTER TABLE doc_exa ADD column_b VARCHAR(20) NULL
GO
EXEC sp_help doc_exa
GO
DROP TABLE doc_exa
GO
B. Alter a table to drop a column
This example modifies a table to remove a column.