Compare Difference Between Null and Blank String in SQL

Null and blank string confuse many people. Today we'll compare the difference between null and empty string to help you better understand them.


By Crystal / Updated on June 30, 2023

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Q: Is a Null Value the Same as a Blank String

Answer: No, a null value is not the same as a blank space.

The concept of NULL and empty string often creates confusion since many people think NULL is the same as a MySQL empty string. However, this is not the case.

What Is Difference Between Null and Blank in SQL

In a database, a null value represents the absence of a value or the lack of a specific data. It is a special marker that indicates that a particular field or attribute does not have a value assigned to it. A null value indicates the absence of data or the unknown status of a data item.

On the other hand, a blank space in a database refers to an empty character or a whitespace character. It is a visible character that represents the absence of a specific character or information within a field or attribute. A blank space is a character that can be stored and retrieved like any other character in a text field.

In a database, null values and blank strings are different in definition, syntax and length, and they are treated differently when querying or manipulating the data.

null vs blank

Which Is Better: Null vs Blank

How would you choose between using null and blank value? Here are some considerations to help you decide which option is better for your specific scenario:

Data Type: Consider the data type of the variable or field. Some programming languages differentiate between null and blank values based on the data type. For example, in languages like Java, null is used for reference types, while blank can be used for primitive types.

Semantics: Think about the meaning and interpretation of the absence of a value in your system. Does it imply the lack of data, or is it more appropriate to indicate an empty or undefined state? Choosing null or blank should align with the intended semantics of your application.

Database and Querying: If you're working with databases, consider how null and blank values are handled during storage and querying. Different database systems may treat null and blank values differently, so ensure consistency in your approach.

Validation: Determine how you want to handle validation and error checking. If a particular field must have a value, using a null or blank value might not be appropriate. In such cases, you may need to enforce stricter validation rules.

Example About the Difference Between Empty String and Null

In table, you can see column phoneNo1 have a null value while PhoneNo2 have an empty value .

difference between null and empty strin

As you know Null value is considered as unknown value and memory is not allocated for it while Empty value is value with empty and memory allocated for it.

Select DptId, DepartmentName, DATALENGTH(PhoneNo1) as PhoneNo1, DATALENGTH(PhoneNo2) as PhoneNo2 from Department


As you can see, PhoneNo1 length in bytes is still null means memory is not allocated to it yet which means that it is unknown value, while phoneNo2 length is zero (0), that means memory is allocated to empty field.

An empty string is useful when the data comes from multiple resources. NULL is used when some fields are optional, and the data is unknown.

Simplify Your SQL Database Backup: Quick and Effective Methods

It is essential to understand the difference between null and empty string to ensure accurate data handling and to avoid potential errors. To better protect your databases in SQL Server, it is also necessary to perform regular database backups.

AOMEI Cyber Backup is a great solution for SQL Server database backup that saves the time and reduces errors of operating individually on different computers.

Automate Backup: schedule backups at specific intervals, such as daily, weekly, or monthly. Users can also set the time and date for each backup.
Incremental Backup: supports incremental backups, which only backup changes made since the last backup, reducing the time and storage required for backups.
Centralized Backup: Run SQL Server Database backups at specific intervals from a centralized console.
Easy-to-use: With the intuitive interface, it's easy to configure SQL backups without script.
Compatibility: supports Microsoft SQL 2005-2022 including SQL Express.

You can use AOMEI Cyber Backup to backup all of your SQL Server within simple steps. Here’s a 30-day free trial for you:

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Centralized and Secure SQL Backup


- Please Download proxy program and install it on to the device with SQL Server installed first. Then, click Already installed proxy and select the device.

- Next, click ... -> Authentication to validate the database instance. You can choose Windows Authentication or SQL Authentication.

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Create Auto SQL Database Backups with Simple Steps

1. Installed AOMEI Cyber Backup and its agent on the server machine. Then navigate to Add Microsoft SQL device.

2. Click Create New Task to launch the task creating page. Choose backup type as Microsoft SQL Backup. As a one-stop and centralized solution, AOMEI Cyber Backup also supports virtual machine backups in a highly efficient and organized manner.

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3. Set up Schedule to run the SQL database backup Daily, Weekly or Monthly, and specify the backup method as Full, Incremental or Differential Backup.

schedule SQL database backup

4. Specify Backup Cleanup plan to delete older backups automatically, thus saving storage space.

5. Once it's finished, you can manage and monitor the backup process in the Backup Task section.

✍ Compared to traditional ways, it’s effortless to restore SQL databases to another server without complicated reinstallation or configuration, which eliminates the need for manual intervention and ensures data consistently.

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This article helps you recognize the nuances between null and empty strings. The main difference between null and empty is that the null is used to refer to nothing while empty is used to refer to a unique string with zero length. Understanding this disparity is crucial for maintaining data accuracy, ensuring efficient programming practices, and avoiding potential pitfalls down the line.

Crystal · Editor
Crystal is an editor from AOMEI Technology. She mainly writes articles about virtual machine. She is a positive young lady likes to share articles with peolpe. Off work she loves travelling and cooking which is wonderful for life.