PostgreSQL
PostgreSQL Joins
Combine related rows from two or more tables.
Why use joins?
A join connects tables through a related key, such as products.category_id and categories.id. The join type determines which unmatched rows remain.
SELECT p.name, c.name AS category
FROM products AS p
JOIN categories AS c ON c.id = p.category_id;Use explicit join conditions so relationships are clear and accidental Cartesian products are avoided.
Further Reading
Continue learning with these related tutorials:
- PostgreSQL Introduction
- PostgreSQL pgAdmin 4
- PostgreSQL Create Table
- PostgreSQL Insert Data
- PostgreSQL Select Data
- PostgreSQL ADD COLUMN
- PostgreSQL UPDATE
- PostgreSQL ALTER COLUMN
- PostgreSQL DROP COLUMN
- PostgreSQL DELETE
- PostgreSQL DROP TABLE
- PostgreSQL Operators
- PostgreSQL SELECT
- PostgreSQL SELECT DISTINCT
- PostgreSQL WHERE
- PostgreSQL ORDER BY
- PostgreSQL LIMIT
- PostgreSQL MIN and MAX
- PostgreSQL COUNT
- PostgreSQL SUM
- PostgreSQL AVG
- PostgreSQL LIKE
- PostgreSQL IN
- PostgreSQL BETWEEN
- PostgreSQL AS
- PostgreSQL Joins
- PostgreSQL INNER JOIN
- PostgreSQL LEFT JOIN
- PostgreSQL RIGHT JOIN
- PostgreSQL FULL JOIN
- PostgreSQL CROSS JOIN
- PostgreSQL UNION
- PostgreSQL GROUP BY
- PostgreSQL HAVING
- PostgreSQL EXISTS
- PostgreSQL ANY
- PostgreSQL ALL
- PostgreSQL CASE
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