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Augustine Madu
Augustine Madu

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All joins in PostgreSQL: Tutorial

This is a comprehensive guide on all the kinds of joins in Postgres and their use cases.

This will equip you with the knowledge to effectively retrieve data across multiple tables in your Postgres database.

What you'll learn:

  • Understanding the concept of joins in relational databases.
  • Types of joins: Inner Join, Left Join, Right Join, Full Outer Join, Self Join, Cross Join, and Natural Join.
  • Practical applications of each join type with real-world scenarios.
  • Writing SQL queries to perform various joins in Postgres.


  • Basic understanding of relational databases.
  • Familiarity with basic SQL syntax.

Video Highlights:

  • Introduction to Joins:
    • Grasp the purpose of joins in retrieving data from multiple tables.
    • Recognize the role of primary and foreign keys in establishing relationships.
  • Types of Joins Explained:
    • Inner Join: Retrieve rows where a match exists in both tables based on the join condition.
    • Left Join: Include all rows from the left table, even if no match is found in the right table (null values are added for unmatched columns).
    • Right Join: Similar to left join, but prioritizes the right table.
    • Full Outer Join: Combine both left and right joins, including unmatched rows from both tables with null values.
    • Self Join: Join a table with itself to compare data within the same table.
    • Cross Join: Produces a Cartesian product, listing all possible combinations of rows from two tables (often used in conjunction with other joins).
    • Natural Join: Automatically joins tables based on columns with identical names.
  • Practical Examples:
    • Employee-Department Database Scenario: Apply different join types to retrieve relevant employee information and their departments.
    • Complex Queries: Explore using joins with multiple tables for intricate data analysis.

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