Question

What are the different modifications that can be made on the structure of a table? Which is the SQL command required for this? Specify the clauses needs for each type of modification.

Answer 1

Alter table command is used to modify existing column or add new column to an existing table. 

There are 2 keywords used

ADD and MODIFY. 

We can alter the table in two ways. 

• We can add a new column to the existing table using the following 

syntax, 

ALTER TABLE

<tablename>ADD(<cloumnname><type><constraint>);

• We can also change or modify the existing column in terms of type or size using the following 

syntax, 

ALTER 

TABLE<tablename>MODIFY<column><newtype>);