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PostgreSQL Joins

Joins combine rows from two or more tables based on related columns. PostgreSQL supports various join types, each serving a distinct purpose in data retrieval.

Key Topics

1. Types of Joins

  • INNER JOIN
  • LEFT JOIN
  • RIGHT JOIN
  • FULL JOIN
  • CROSS JOIN

2. Basic Join Syntax

SELECT t1.column, t2.column
FROM table1 t1
[JOIN_TYPE] JOIN table2 t2
    ON t1.common_column = t2.common_column;

Replace [JOIN_TYPE] with the desired type (INNER, LEFT, RIGHT, FULL, CROSS).

Best Practices

  • Pick the appropriate join type based on how you want unmatched rows handled.
  • Always specify the join condition in the ON clause (except for cross joins).

Key Takeaways

  • Joins are fundamental for combining data from multiple tables.
  • Different join types control whether unmatched rows are included or excluded.
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