'Joins' are used to get data from two or more tables which are joined on a certain relationship between specified columns present in the tables being queried.

• Cross Join
• Inner Join
• Outer Join
• Left Outer Join
• Right Outer Join
• Full Outer Join
• Self Join

SQL Cross Join

The 'SQL Joins ' are cartesian products that join everything to everything ie. each row of table A is joined to each row of table B. So if table A has 5 rows of data and table B has 6 rows of data, then you get a cartesian product of 5x6= 30 rows of data. So you can see why this is a very dangerous join to run against large tables.

SQL 'Cross Join' Syntax

The Cross Join Example

The 'Employees' table contains their respective data as shown below.



The 'Department' table contains the following columns and their respective data type as shown above.


Note : In a Cross Join, the where clause is absent. If present, it then functions like a Inner Join which we will discuss in the following chapters. We will be using an alias name as there are two tables being used here and they both have a common column.




Note: Since there are 10 records in the Employees table and 6 records in the Department table, it combines to form 60 records in this case.