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INNER JOIN - (PostgreSQL Join)

The INNER JOIN operation is used in PostgreSQL to combine rows from two or more tables based on a related column between them. In this tutorial, we'll discuss the syntax, example, output, explanation, use, important points, and summary of the INNER JOIN operation in PostgreSQL.

Syntax

SELECT column_name(s)
FROM table1
INNER JOIN table2
ON table1.column_name = table2.column_name;
  • column_name(s): The column name or names to select from one or both tables.
  • table1 and table2: The names of the tables to join.
  • column_name: The name of the column that is present in both tables and used as the basis for the join.

Example

Let's take an example of using the INNER JOIN operation to combine data from two tables.

SELECT orders.order_id, customers.customer_name, orders.order_date
FROM orders
INNER JOIN customers
ON orders.customer_id = customers.customer_id;

The output of this query would look something like this:

order_id |  customer_name   |  order_date
---------+------------------+------------
   10248 | Alfreds Futterk. | 1996-07-04
   10249 | Ana Trujillo Emp. | 1996-07-05
   10250 | Antonio Moreno   | 1996-07-08
   10251 | Around the Horn  | 1996-07-08
   10252 | Berglunds snabbk. | 1996-07-09
   10253 | Blauer See Delikatessen | 1996-07-10
      .           .                  .
      .           .                  .
      .           .                  .

Explanation

In the above example, we used the INNER JOIN operation to combine data from two tables: orders and customers. We selected the order_id and order_date columns from the orders table and the customer_name column from the customers table.

We then joined the two tables on the customer_id column, which was present in both tables.

Use

The INNER JOIN operation is used to combine data from two or more related tables into a single result set. This is useful when you need to retrieve data that is spread across multiple tables.

Important Points

  • The column used to join the tables should be present in both tables.
  • The INNER JOIN operation only returns rows that have matching values in both tables.
  • It is possible to join more than two tables using the INNER JOIN operation.

Summary

In this tutorial, we discussed the INNER JOIN operation in PostgreSQL. We covered the syntax, example, output, explanation, use, and important points of the INNER JOIN operation. With this knowledge, you can now use the INNER JOIN operation to combine data from two or more tables into a single result set in your PostgreSQL queries.

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