How to Avoid Division By Zero in PostgreSQL?

In PostgreSQL, attempting to divide by zero results in an error that can disrupt queries, making it essential to handle this scenario effectively. Fortunately, PostgreSQL provides several techniques for preventing the division by zero error. By Using functions like NULLIF(), COALESCE(), and CASE statements, we can avoid this error and ensure smooth database operations.

In this article, we’ll explain several methods to handle division by zero in PostgreSQL, each with practical examples and outputs. This guide will help us manage error-free arithmetic calculations, improving database reliability and accuracy.

Understanding the Division by Zero Error in PostgreSQL

In PostgreSQL, we can perform arithmetic operations like addition, subtraction, multiplication, and division. When an integer is divided by Zero it throws a zero division error and we have to solve the zero division error by ourselves in PostgreSQL.

Dividing by zero produces a runtime error that stops query execution, typically displaying an error message. This error can be problematic especially in production systems, where even minor interruptions can impact database performance.

Methods to Handle Division by Zero in PostgreSQL

Some methods are useful to handle zero division error, and for that, we should have some sound knowledge of working with PostgreSQL. So, now let's look into these methods to handle this obnoxious zero-division error. There are methods available that are super useful for handling zero-division errors. Some of the methods are as follows:

1. Using NULLIF() Function
   
2. Using Case Statement to Handle Zero Division Error

Look at the below image to understand what zero zero-division error looks like.

Explanation:

As we can see in the above image, when we try to divide 10 by Zero we get an error, but handling these errors is important. When working on large projects it is important to solve this arithmetic error or it will create confusion later on.

1. Handling Division by Zero Using NULLIF()

In Postgres, the NULLIF function takes two expressions and returns NULL if they are equal instead of throwing an error and if they are not equal it will return the first expression. Now let's look into the syntax of NULLIF() and then we will going to use that to handle zero division error.

Syntax

NULLIF(Expression_1, Expression_2)

• If Expression 1 == Expression2 then, return NULL
• If Expression 1 != Expression 2 then, return Expression 1

Example 1: Handling Division by Zero with NULLIF()

We are going to use NULLIF() to handle zero division errors and then see different examples to use this function using our records in the table and see how we can use NULLIF() to handle zero division errors while doing arithmetic operations in this example.

Query:

SELECT 10 / NULLIF(0,0)

Output

Explanation:

• As we can see, we don't get a zero division error this time. Here Expression 1 is zero and Expression 2 is also Zero thus we get NULL value in return.
  
• But here, we are facing a problem, as we got a NULL value we can not output anything at all. It is just showing a NULL value.
  
• To solve this issue we have to use a Keyword called COALESCE.

Using COALESCE() with NULLIF() to Provide a Default Value

Here we are not able to print results after handling zero division error. To overcome this issue we have to use COALESCE. It allows to have a default value in case the first one is not present or not available. We are going to use this with our NULLIF() and then we will understand it better.

Example 2: Handling Division by Zero with NULLIF() and COALESCE()

In this example, the NULLIF() function returns NULL when attempting to divide by zero, preventing an error. COALESCE() then substitutes the NULL with a specified default value (0), ensuring a safe, error-free result.

Query:

SELECT COALESCE ( 10 / NULLIF(0,0), 0 );

Output

Explanation:

• Now, we have successfully handled zero division errors using COALESCE() and NULLIF().
  
• Here, we have passed two arguments in COALESCE(), first argument is "10 / NULLIF(0,0)". The second argument we have passed is "0".
  
• As COALESCE() returns first not NULL value, and here "NULLIF(0,0)" returns 0.
  
• So COALESCE() neglects the value returned by NULLIF(0,0) that is NULL, and returns the value given in the 2nd argument which is value "0".
  
• That's why we got "0" instead of NULL this time.

2. Handling Division by Zero Using CASE Statements

The case statement is useful for handling zero-division errors when we are working with records. Let's look into the syntax of the case statement and then work with it to handle zero division errors.

Syntax:

CASE
WHEN condition..1 THEN result..1
WHEN condition..2 THEN result ..2
END

Example 1: Using CASE Statements to Handle Division by Zero

Here in this example, we are going to use records to calculate results and handle zero division error for that we have to create a table.

1. Create a Sample Table

CREATE TABLE maths(numerator INT, denominator INT);

2. Insert Sample Data

INSERT INTO maths(numerator,denominator) VALUES(12,2);
INSERT INTO maths(numerator,denominator) VALUES(21,0);
INSERT INTO maths(numerator,denominator) VALUES(10,3);
INSERT INTO maths(numerator,denominator) VALUES(15,0);

Output

3. Query with CASE Statement

Now we are going to use the CASE statement with this table to calculate the values and tackle zero division error. Enter the below query to get the results also tackling zero division error.

SELECT numerator, denominator, CASE
WHEN denominator <= '0' then 0
WHEN denominator > '0' THEN numerator/denominator
END AS ans 
FROM maths;

Output

Explanation:

• We are using the CASE statement here to match the condition and execute the related result.
  
• Here to handle zero division error, we check the case if the "denominator <= '0' " then it will return "0" not the error.
  
• And, name the column "and" to display the results.

Conclusion

Handling division by zero errors in PostgreSQL is essential to prevent disruptions in query execution and to maintain data integrity. By using NULLIF(), COALESCE(), and CASE statements, we can effectively avoid division by zero errors and ensure accurate query results. The methods covered in this guide allow us to gracefully handle division errors, providing flexibility and reliability in database operations.

ujjwal_gupta

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Article Tags :

• PostgreSQL
• Databases
• PostgreSQL Query