SQL ALTER TABLE Keyword
ALTER TABLE
The ALTER TABLE command adds, deletes, or 
modifies columns in a table.
The ALTER TABLE command also adds and 
deletes various constraints in a table.
The following SQL adds an "Email" column to the "Customers" table:
Example
  ALTER TABLE Customers
ADD Email varchar(255);
The following SQL deletes the "Email" column from the "Customers" table:
Example
  ALTER TABLE Customers
DROP COLUMN Email;
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