One can opt to choose any setup of PostgreSQL on any hosting platform including installation and setup on a local machine. For simplicity, we would be using Azure Database for PostgreSQL on the Microsoft Azure cloud. Many cloud vendors offer a managed version of PostgreSQL on the cloud. PostgreSQL is an open-source relational database and there are various ways of installing and configuring it. There are multiple types of PostgreSQL Joins that can be used to extract data for different types of scenarios. The technical term for relating data while querying data from a set of tables is known as “join”. Due to this relational and inter-linked nature of the data model, which is implemented in the form of tables, it becomes inevitable to extract data from multiple tables and then relate this data together from a result set that is requested by the consuming application. Relational databases are generally used to store data in database objects known as tables which are modeled in a normalized fashion for several reasons like data deduplication, better organization of data, modeled entity relationships, etc. One of the most popular open-source relational databases is PostgreSQL. There are various industry-leading database systems available in the industry. ![]() In this tutorial, you have learned about the PostgreSQL NATURAL JOIN works and how to use it to query data from two or more tables that have the common columns.In this article, we will learn about different types of PostgreSQL joins with examples.ĭata is generally hosted in a variety of data management repositories, one of them being relational database management systems. However, the NATURAL JOIN clause just uses the last_update column. NATURAL JOIN country Code language: SQL (Structured Query Language) ( sql )īoth tables also have another common column called last_update, which cannot be used for the join. However, you should avoid using the NATURAL JOIN whenever possible because sometimes it may cause an unexpected result.įor example, See the following city and country tables from the sample database:īoth tables have the same country_id column so you can use the NATURAL JOIN to join these tables as follows: SELECT * The convenience of the NATURAL JOIN is that it does not require you to specify the join clause because it uses an implicit join clause based on the common column. INNER JOIN categories USING (category_id) Code language: SQL (Structured Query Language) ( sql ) The above statement is equivalent to the following statement that uses the INNER JOIN clause. NATURAL JOIN categories Code language: SQL (Structured Query Language) ( sql ) The following statement uses the NATURAL JOIN clause to join the products table with the categories table: SELECT * FROM products ( 'Kindle Fire', 3) Code language: SQL (Structured Query Language) ( sql ) INSERT INTO products (product_name, category_id) The following INSERT statements insert some data into the categories and products tables. The category_id is the common column that we will use to perform the natural join. The category_id column in the products table is the foreign key that references to the primary key of the categories table. ![]() ) Code language: SQL (Structured Query Language) ( sql )Įach category has zero or many products and each product belongs to one and only one category. ![]() DROP TABLE IF EXISTS categories įOREIGN KEY (category_id) REFERENCES categories (category_id) The following CREATE TABLE statements create the categories and products tables. To demonstrate the PostgreSQL natural join, we will create two tables: categories and products.
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