Which command is used to remove an index from the database in SQL?

The correct answer is Option 4) DROP INDEX.

Key Points

• The DROP INDEX command is used in SQL to remove an existing index from a table.
• It deletes the index permanently from the database, freeing up space and resources.
• Syntax (for MySQL):
  DROP INDEX index_name ON table_name;
• Syntax (for SQL Server):
  DROP INDEX table_name.index_name;
• Indexes help speed up query performance, but unnecessary or unused indexes can be dropped to improve database efficiency.

Additional Information 

• Incorrect Options:
  • ROLL BACK INDEX: No such command exists in SQL. ROLLBACK is used to undo transactions, not to drop indexes.
  • DELETE INDEX: DELETE is used for deleting records from a table, not indexes.
  • REMOVE INDEX: Not a valid SQL command for dropping indexes.
• Always ensure that the index is no longer required before dropping it to avoid performance issues in future queries.