ALTER TABLE
===========

An ALTER statement modifies the definition (structure) of a table inside Drizzle. 
The types of objects that can be altered depends on which RDBMS is being used. 

The ALTER TABLE statement is used to change a table definition by: 

1) Adding, dropping, modifying table columns 
2) Adding and dropping constraints 
3) Enabling and Disabling constraints 
4) Rename a table

.. todo::

   add something about current implementation: i.e. write blocking copying alter table.
