Which of the SQL command is used to change the structure of a table after it has been created?UPDATEALTERDROPTRUNCATENone of the above

The SQL command used to change the structure of a table after it has been created is the ALTER command. The ALTER TABLE statement allows you to modify an existing table’s structure, such as adding, deleting, or modifying columns and constraints.

Here’s a brief overview of other options mentioned:

1. UPDATE: This command is used to modify existing records in a table, not the table structure.
2. DROP: This command deletes an entire table from the database.
3. TRUNCATE: This command removes all records from a table but does not change the table structure.
4. None of the above: This option is incorrect because the ALTER command is the right choice.

In summary, if you need to change the structure of a table, the correct command to use is ALTER.