First Guide to SQL Anywhere Studio
   PART 3. Basic SQL
     CHAPTER 13. Joining Tables       

Joining tables with the cross product

One of the tables in the sample database is sales_order, which lists the orders placed to the company. Each order has a sales_rep column, containing the employee ID of the sales representative responsible for the order. There are 648 rows in the sales_order table.

You can get information from two tables at the same time by listing both tables in the FROM clause of a SELECT query.

Example 

The following example lists all the data in the employee table and the sales_order table:

SELECT *
FROM sales_order CROSS JOIN employee

The results of this query, displayed in the Interactive SQL data window, match every row in the employee table with every row in the sales_order table. Since there are 75 rows in the employee table and 648 rows in the sales_order table, there are 75 ( 648 = 48,600 rows in the result of the join. Each row consists of all columns from the sales_order table followed by all columns from the employee table. This join is called a full cross product.

The cross product join is a simple starting point for understanding joins, but not very useful in itself.