Which operation changes the structure of an existing table?

• A. Update
• B. Create Table
• C. Delete From
• D. Alter Table

Answer: (D)

Changing the structure of an existing table is done with ALTER TABLE. This command modifies the table’s schema—adding or dropping columns, changing a column’s data type, adjusting constraints, or even renaming the table. It’s about the table’s definition, not the data itself.

Update changes values inside existing rows, Delete From removes rows, and Create Table builds a new table with its own schema, so they don’t alter the structure of an existing table.