Intro to SQL Joins

Objectives

• Explain the order & structure of join statements
• Write basic SQL joins: one-to-many
  • INNER join
  • LEFT join
  • FULL OUTER join
• Write basic SQL joins that only select certain fields
  • INNER join
  • LEFT join

Instructions

1. Create a database called joins
2. Connect to joins database using psql
3. Run joins.sql file while connected to db:

• \i joins.sql

INNER JOIN going from 'owner' to 'pet'

SELECT * FROM owner INNER JOIN pet ON pet.owner_id = owner.id;

LEFT JOIN

SELECT * FROM owner LEFT JOIN pet ON pet.owner_id = owner.id;

Resources

• Learn - Joins Syntax
• Visual Representation of SQL Joins