Doc. Comment. Xchange. PostgreSQL INNER JOIN to join 3 tables example. The following diagram illustrates the relationship between three tables staff, payment, and customer. SQL Using Joins. The SQL Joins clause is used to combine records from two or more tables in a database. A JOIN is a means for combining fields from two tables by using values common to each. Consider the following two tables Table 1 CUSTOMERS Table. ID NAME AGE ADDRESS SALARY. Ramesh 3. 2 Ahmedabad 2. Khilan 2. 5 Delhi 1. Kota 2. 00. 0. Chaitali 2. Mumbai 6. Hardik 2. Plight Of The Zombie Final Dance. Bhopal 8. Komal 2. MP 4. Muffy 2. 4 Indore 1. Dependencies. web2py comes with a Database Abstraction Layer DAL, an API that maps Python objects into database objects such as queries, tables, and records. Update Statement With Inner Joins 3' title='Update Statement With Inner Joins 3' />Table 2 ORDERS Table. OID DATE CUSTOMERID AMOUNT. Now, let us join these two tables in our SELECT statement as shown below. Update Statement With Inner Joins 3' title='Update Statement With Inner Joins 3' />SQL SELECT ID, NAME, AGE, AMOUNT. FROM CUSTOMERS, ORDERS. WHERE CUSTOMERS. ID ORDERS. CUSTOMERID. This would produce the following result. ID NAME AGE AMOUNT. Khilan 2. 5 1. Chaitali 2. Here, it is noticeable that the join is performed in the WHERE clause. Several operators can be used to join tables, such as, lt, lt, lt, BETWEEN, LIKE, and NOT they can all be used to join tables. However, the most common operator is the equal to symbol. There are different types of joins available in SQL INNER JOIN returns rows when there is a match in both tables. LEFT JOIN returns all rows from the left table, even if there are no matches in the right table. RIGHT JOIN returns all rows from the right table, even if there are no matches in the left table. FULL JOIN returns rows when there is a match in one of the tables. SELF JOIN is used to join a table to itself as if the table were two tables, temporarily renaming at least one table in the SQL statement. CARTESIAN JOIN returns the Cartesian product of the sets of records from the two or more joined tables. Let us now discuss each of these joins in detail.