CROSS JOIN

-- Use CROSS JOIN to generate all combinations.
SELECT column_name, ...
FROM table1
CROSS JOIN table2;

-- A comma-separated FROM clause produces the same result (older style).
SELECT column_name, ...
FROM table1, table2;

-- Generate all combinations of the products table and the colors table.
SELECT
    s.product_name,
    c.color
FROM products AS s
CROSS JOIN colors AS c;

-- Combine a days-of-week table and a time-slot table to build a shift schedule grid.
SELECT
    d.day_of_week,
    t.time_slot
FROM days AS d
CROSS JOIN time_slots AS t
ORDER BY d.day_id, t.slot_id;

-- products (3 rows) × colors (4 rows) = 12 rows returned.
product_name | color
-------------+-------
T-Shirt      | Red
T-Shirt      | Blue
T-Shirt      | Green
T-Shirt      | White
Hoodie       | Red
Hoodie       | Blue
Hoodie       | Green
Hoodie       | White
Jacket       | Red
Jacket       | Blue
Jacket       | Green
Jacket       | White

The CROSS JOIN syntax is supported across all major databases.

-- Common to MySQL, PostgreSQL, SQL Server, Oracle, and SQLite
SELECT s.product_name, c.color
FROM products AS s
CROSS JOIN colors AS c;

In Oracle, the older comma-separated syntax (FROM table1, table2) is also widely used. It behaves identically to CROSS JOIN, but using CROSS JOIN explicitly is recommended for clarity.

CROSS JOIN is a join with no join condition — it pairs every row in the left table with every row in the right table. The number of result rows equals the left table row count multiplied by the right table row count.

Common use cases include generating calendars, building shift schedule grids, and listing all size-and-color combinations — any situation where you intentionally need every possible pairing. Using CROSS JOIN on large tables can cause the row count to explode, so check the expected number of rows before running the query.

For the basics of joins, see INNER JOIN. To join a table to itself, see SELF JOIN.