Which statement creates an index on orders(customer_id) with the name idx_orders_customer_id?

• A. CREATE UNIQUE INDEX idx_orders_customer_id ON orders (customer_id)
• B. CREATE INDEX ON orders (customer_id)
• C. CREATE INDEX idx_orders_customer_id ON orders (customer_id)
• D. CREATE INDEX idx_orders_customer_id ON customers (customer_id)

Answer: (C)

Creating a named non‑unique index on a table uses the pattern: CREATE INDEX index_name ON table_name (column_list). Here, the index name is provided as idx_orders_customer_id, the target table is orders, and the column to index is customer_id. This exactly matches the requirement to create an index on orders(customer_id) with that name, and it yields a standard non-unique index suitable for lookups by customer_id.

If you used UNIQUE, you’d enforce that each customer_id appears only once in orders, which would prevent multiple orders for the same customer—usually not desired. If you omit the index name, many systems require a name. If you point to a different table, like customers, you’d be indexing the wrong table.