Make queries faster.
✍️ 3 exercises + code challenge in this lessonAn index is a lookup structure that helps the database find rows quickly, like the index at the back of a book.
CREATE INDEX idx_city ON Customers (City);CREATE UNIQUE INDEX also enforces uniqueness.DROP INDEX idx_city;Index columns you often use in WHERE, JOIN and ORDER BY. But every index slows down inserts and updates slightly, so do not index everything.
Mastering SQL Indexes helps you write clean and reliable SQL code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.
CREATE INDEX idx_customers_city ON Customers (City);
EXPLAIN QUERY PLAN
SELECT * FROM Customers WHERE City = 'Lahore';
SELECT name, tbl_name FROM sqlite_master WHERE type = 'index';Check what you learned in “SQL Indexes”.
Create an index on the City column.
idx_city ON Customers (City);
What is the downside of having many indexes?
Create an index idx_price on Products(Price), then list index names from sqlite_master where type = 'index' and tbl_name = 'Products'.
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