How to JOIN Tables in DB2: SQL Query

Relational databases use JOIN operations to combine data from different tables for analysis. DB2, a popular database management system, offers powerful JOIN functionalities. In this blog post, we will explore the types, syntax, and examples of DB2 JOIN operations. By the end, you will have the knowledge to effectively use JOINs in DB2 for data retrieval and analysis.

DB2 Join SQL Query — Photo by Teona Swift on Pexels.com

Join in DB2

In this article, we will cover:

Understanding the fundamentals of JOIN operations in DB2.
Examining practical scenarios using SQL query to perform JOIN operations with step-by-step explanations.

Here are two tables. Employees” and “Departments”. Then run the JOIN SQL query to retrieve the required information.

Employees Table:

EmployeeID	FirstName	LastName	DepartmentID
1	John	Doe	101
2	Jane	Smith	102
3	Robert	Johnson	101
4	Emily	Brown	103
5	Michael	Lee	102

Table 1

Departments Table:

DepartmentID	DepartmentName	ManagerID
101	HR	1
102	IT	2
103	Finance	4

Table 2

Join SQL Query

SELECT e.EmployeeID, e.FirstName, e.LastName, d.DepartmentName, m.FirstName AS ManagerFirstName, m.LastName AS ManagerLastName 
FROM Employees e 
JOIN Departments d 
ON e.DepartmentID = d.DepartmentID 
JOIN Employees m ON d.ManagerID = m.EmployeeID;

Result:

EmployeeID	FirstName	LastName	DepartmentName	ManagerFirstName	ManagerLastName
1	John	Doe	HR	John	Doe
2	Jane	Smith	IT	Jane	Smith
3	Robert	Johnson	HR	John	Doe
4	Emily	Brown	Finance	Emily	Brown
5	Michael	Lee	IT	Jane	Smith

Result

In the above query, we used JOIN operations to connect the “Employees” and “Departments” tables twice. The first JOIN connects the tables based on the “DepartmentID” column, and the second JOIN connects the tables based on the “ManagerID” and “EmployeeID” columns to retrieve the names of the department managers.

As a result, we get a list of all employees with their respective department names and the names of their department managers.

SQL Bootcamp

>>Buy NOW

Srini

Data Engineer with deep AI and Generative AI expertise, crafting high-performance data pipelines in PySpark, Databricks, and SQL. Skilled in Python, AWS, and Linux—building scalable, cloud-native solutions for smart applications.