Equi Join - (Oracle Joins)

In Oracle database, an equi join is a type of join that is used to combine data from two tables where the data in one or more columns matches. The matching columns are called the join columns.

Syntax

The syntax for performing an equi join using the JOIN keyword in Oracle is as follows:

SELECT column1, column2, ...
FROM table1 JOIN table2
ON table1.column = table2.column;

Here, column1, column2, ... are the columns you want to select from the tables, table1 and table2 are the tables you want to join, and column is the column that will be used for the join.

Example

Here is an example of performing an equi join in Oracle:

SELECT employees.first_name, employees.last_name, departments.department_name
FROM employees
JOIN departments
ON employees.department_id = departments.department_id;

Output

FIRST_NAME  LAST_NA DEPARTMENT_NAME
----------- ------- ------------------------------
Steven      King    Executive
Neena       Kochhar Executive
Lex         De Haan Executive
Alexander   Hunold  IT
Bruce       Ernst   IT
David       Austin  IT
Valli       Pataballa       IT
Diana       Lorentz IT
Nancy       Greenberg       Finance
Daniel      Faviet  Finance

Explanation

In the above example, we have joined the employees and departments tables using the department_id column as the join column. We have selected the first_name and last_name columns from the employees table and the department_name column from the departments table.

Use

Equi joins are useful for combining data from two or more tables where the data in one or more columns matches. They are used to retrieve data that is spread across multiple tables in a database.

Important Points

• Equi join is a join in which the matching columns have the same name and data type in both tables.
• The JOIN keyword is used to perform an equi join in Oracle.
• The join column is specified using the ON keyword.

Summary

In summary, equi join is a type of join used in Oracle to combine data from two tables where the matching columns have the same name and data type. They are useful for combining data from multiple tables in a database.