SQL (Structured Query Language) is a powerful language used for managing and manipulating relational databases. Within SQL, conditional statements are essential for specifying the logic and flow of operations. In this blog post, we will explore how to write conditional statements in SQL Command Line Interface (CLI) to handle various scenarios and make our queries more flexible and dynamic.

Table of Contents

1. Introduction
2. IF-ELSE Statements
3. CASE Statements
4. Conclusion

Introduction

In SQL CLI, the most commonly used conditional statements are IF-ELSE and CASE statements. These statements allow us to execute different sets of SQL statements based on specific conditions or evaluate expressions to return different results. Let’s dive into each type of statement and see how they can be used.

IF-ELSE Statements

The IF-ELSE statement in SQL CLI is used to conditionally execute a block of SQL code based on a specified condition. The basic syntax of an IF-ELSE statement is as follows:

IF condition
   statement(s);
ELSE
   statement(s);
END IF;

Here’s an example to demonstrate the usage of IF-ELSE statement:

IF (SELECT COUNT(*) FROM employees) > 0
   SELECT * FROM employees;
ELSE
   PRINT 'No employees found.';
END IF;

In the above example, if the number of rows in the employees table is greater than 0, it retrieves all the employee records. Otherwise, it prints a message indicating that no employees were found.

CASE Statements

The CASE statement in SQL CLI is used to perform conditional branching based on a specific value or expression. It allows us to evaluate different conditions and return different values based on the result. The basic syntax of a CASE statement is as follows:

CASE
   WHEN condition_1 THEN result_1
   WHEN condition_2 THEN result_2
   ...
   ELSE result_n
END;

Here’s an example to illustrate the usage of the CASE statement:

SELECT department_name,
       CASE
          WHEN department_id > 50 THEN 'Large Department'
          WHEN department_id > 20 THEN 'Medium Department'
          ELSE 'Small Department'
       END AS department_size
FROM departments;

In the above example, the CASE statement evaluates the department_id and assigns a corresponding department_size value based on the condition. This provides a custom column “department_size” indicating whether the department is large, medium, or small.

Conclusion

Conditional statements in SQL CLI, such as IF-ELSE and CASE, allow us to handle different scenarios and make our queries more dynamic and flexible. By utilizing these statements effectively, we can control the flow of execution and return relevant results based on specific conditions. Incorporating conditional logic into our SQL queries helps us create more powerful and adaptable database operations.

Remember to experiment with the provided examples and take advantage of the various conditional statements available in SQL CLI. Happy coding!

Tags: #SQL #CLI