Skip to main content

11

sql

-- Create the students table
CREATE TABLE students (
  id INTEGER PRIMARY KEY,
  name TEXT,
  grade INTEGER
);

-- Insert sample data
INSERT INTO students (name, grade) VALUES
  ('Alex', 92),
  ('Sara', 85),
  ('Daniel', 90),
  ('Mia', 78),
  ('John', 95);

-- 1. Create an index for faster lookups by name
CREATE INDEX idx_student_name ON students(name);

-- 2. Avoid SELECT *: fetch only needed columns
SELECT name, grade FROM students;

-- 3. Use EXPLAIN QUERY PLAN to analyze performance
EXPLAIN QUERY PLAN
SELECT name FROM students WHERE grade > 90;

-- 4. Example of filtering before joining
SELECT *
FROM (SELECT * FROM orders WHERE status = 'paid') AS o
JOIN customers c ON o.customer_id = c.id;

-- 5. Use LIMIT during development
SELECT * FROM orders LIMIT 100;

Want to learn more?

Join CodeFriends Plus membership or enroll in a course to start your journey.

sql