MS SQL: query to add column

ALTER TABLE {TABLENAME}
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL}
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}

i.e:

ALTER TABLE Protocols ADD ProtocolTypeID int NOT NULL DEFAULT(1);

 
Source:
http://stackoverflow.com/questions/92082/add-column-with-default-value-to-existing-table-in-sql-server