How do B-Tree indexes work in SQLite and what is a Covering Index?

Explanation & Concept

SQLite uses B-Tree indexes to accelerate lookups. When an index contains all the columns needed by a query (a Covering Index), SQLite satisfies the query entirely from the index B-Tree without seeking the main table data pages.

Code Example

sql

-- Create covering index
CREATE INDEX idx_orders_customer_date_total 
ON orders (customer_id, order_date, total);

-- Query covered completely by index (zero table page reads)
SELECT order_date, total 
FROM orders 
WHERE customer_id = 99;

How It Works & Key Takeaways

Because `customer_id`, `order_date`, and `total` all reside inside `idx_orders_customer_date_total`, SQLite avoids the secondary lookup into the `orders` row storage.

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How do B-Tree indexes work in SQLite and what is a Covering Index?

Explanation & Concept

Code Example

sql

-- Create covering index
CREATE INDEX idx_orders_customer_date_total 
ON orders (customer_id, order_date, total);

-- Query covered completely by index (zero table page reads)
SELECT order_date, total 
FROM orders 
WHERE customer_id = 99;

How It Works & Key Takeaways

Because `customer_id`, `order_date`, and `total` all reside inside `idx_orders_customer_date_total`, SQLite avoids the secondary lookup into the `orders` row storage.

Mock Test · 1 Questions · Optional

Ready for Foreign Keys?

Take a quick test to evaluate yourself, or move straight to the next module.

Beginner1 questions

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