TSQL: ALTER TABLE

--Alter table
ALTER TABLE MyTable ALTER COLUMN NullCOl NVARCHAR(20) NOT NULL
ALTER TABLE doc_exa ADD column_b VARCHAR(20) NULL
ALTER TABLE doc_exb DROP COLUMN column_b
ALTER TABLE doc_exc ADD column_b VARCHAR(20) NULL CONSTRAINT exb_unique UNIQUE
ALTER TABLE doc_exd WITH NOCHECK ADD CONSTRAINT exd_check CHECK (column_a > 1)