Hits: 12
(SQL tutorials for Business Analyst & Beginners)
In this end-to-end example, you will learn – SQL Tutorials for Business Analyst: SQL | SELF JOINS.
The SQL 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.
Syntax
The basic syntax of SELF JOIN is as follows −
SELECT a.column_name, b.column_name... FROM table1 a, table1 b WHERE a.common_field = b.common_field;
Here, the WHERE clause could be any given expression based on your requirement.
Example
Consider the following table.
CUSTOMERS Table is as follows.
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
Now, let us join this table using SELF JOIN as follows −
SQL> SELECT a.ID, b.NAME, a.SALARY FROM CUSTOMERS a, CUSTOMERS b WHERE a.SALARY < b.SALARY;
This would produce the following result −
+----+----------+---------+ | ID | NAME | SALARY | +----+----------+---------+ | 2 | Ramesh | 1500.00 | | 2 | kaushik | 1500.00 | | 1 | Chaitali | 2000.00 | | 2 | Chaitali | 1500.00 | | 3 | Chaitali | 2000.00 | | 6 | Chaitali | 4500.00 | | 1 | Hardik | 2000.00 | | 2 | Hardik | 1500.00 | | 3 | Hardik | 2000.00 | | 4 | Hardik | 6500.00 | | 6 | Hardik | 4500.00 | | 1 | Komal | 2000.00 | | 2 | Komal | 1500.00 | | 3 | Komal | 2000.00 | | 1 | Muffy | 2000.00 | | 2 | Muffy | 1500.00 | | 3 | Muffy | 2000.00 | | 4 | Muffy | 6500.00 | | 5 | Muffy | 8500.00 | | 6 | Muffy | 4500.00 | +----+----------+---------+
Free Machine Learning & Data Science Coding Tutorials in Python & R for Beginners. Subscribe @ Western Australian Center for Applied Machine Learning & Data Science.
Western Australian Center for Applied Machine Learning & Data Science – Membership
Sign up to get end-to-end “Learn By Coding” example.
Introduction to Applied Machine Learning & Data Science for Beginners, Business Analysts, Students, Researchers and Freelancers with Python & R Codes @ Western Australian Center for Applied Machine Learning & Data Science (WACAMLDS) !!!
Latest end-to-end Learn by Coding Projects (Jupyter Notebooks) in Python and R:
Applied Statistics with R for Beginners and Business Professionals
Data Science and Machine Learning Projects in Python: Tabular Data Analytics
Data Science and Machine Learning Projects in R: Tabular Data Analytics
Python Machine Learning & Data Science Recipes: Learn by Coding