alter table oracle

1ALTER TABLE tablename MODIFY columnname varchar2(100)

1ALTER TABLE table_name
2  RENAME COLUMN old_name TO new_name;

1{
2    UPDATE table-Name [[AS] correlation-Name]
3        SET column-Name = Value
4        [ , column-Name = Value} ]*
5        [WHERE clause] |
6    UPDATE table-Name
7        SET column-Name = Value
8        [ , column-Name = Value ]*
9        WHERE CURRENT OF
10}

1ALTER TABLE products
2ADD CONSTRAINT fk_supplier
3  FOREIGN KEY (supplier_id)
4  REFERENCES supplier(supplier_id);

1ALTER TABLE table_name
2ADD CONSTRAINT constraint_name
3   FOREIGN KEY (column1, column2, ... column_n)
4   REFERENCES parent_table (column1, column2, ... column_n);