Indexes

Study the pattern

Indexes may speed lookups but add storage and write overhead. Predict the output before running the example.

CREATE INDEX idx_orders_customer ON orders(customer_id);

Explain it from memory

What does today's SQL feature do, and when would you use it?

Use CREATE INDEX index_name ON table(column).

Run SQL in your browser

Run the example, then modify one clause and predict how the result changes.

Use CREATE INDEX index_name ON table(column).

Consolidate the skill

• Run and inspect the output.
• Change one part and predict the difference.
• Return later and rewrite the query from memory.