The ALTER VIEW format varies according to the RDBMS system: 
DB2 Format:

          ALTER VIEW view_table_name
          ALTER [COLUMN] column_name ADD SCOPE type
            ...;

Oracle Format:

          ALTER VIEW view_table_name
           {ADD CONSTRAINT constraint_clause
       | MODIFY CONSTRAINT constraint_clause
         | DROP CONSTRAINT constraint_clause};

SQL Server Format:

          ALTER VIEW view_table_name [column[,...]]
          [WITH {ENCRYPTION | SCHEMABINDING | VIEW_METADATA}];

> DB2 will not allow you to DROP a column.

> MySQL 5 supports views but earlier versions of MySQL do not support views.

> PostgreSQL has limited support options.