Which command is used to change the structure of an existing table in SQL?
a) ALTER
b) MODIFY
c) UPDATE
d) INSERT
Answer:
a) ALTER
Explanation:
The ALTER command in SQL is used to modify the structure of an existing table. It can be used to add, delete, or modify columns, as well as to add or drop constraints such as primary keys or foreign keys.
For example, ALTER TABLE employees ADD email VARCHAR(50) would add a new column named “email” to the “employees” table.
ALTER is commonly used when changes need to be made to the database schema without affecting the data stored in the table.