W3Schools
w3schools.com โบ sql โบ sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
SQL Examples SQL Editor SQL Quiz SQL Exercises SQL Server SQL Syllabus SQL Study Plan SQL Bootcamp SQL Certificate SQL Training ... If a field in a table is optional, it is possible to insert or update a record without adding any value to this field. This way, the field will be saved with a NULL value. A NULL value represents an unknown, missing, or inapplicable data in a database ...
special marker and keyword in SQL indicating that something has no value
Factsheet
Null (SQL)
Notation ฯ
Null (SQL)
Notation ฯ
Wikipedia
en.wikipedia.org โบ wiki โบ Null_(SQL)
Null (SQL) - Wikipedia
January 7, 2026 - This is not true for all database implementations. In an Oracle RDBMS, for example, NULL and the empty string are considered the same thing and therefore 'Fish ' || NULL || 'Chips' results in 'Fish Chips'. Since Null is not a member of any data domain, it is not considered a "value", but rather a marker (or placeholder) indicating the undefined value.
HistoryNull propagationComparisons with NULL and the three-valued logic (3VL)Analysis of SQL Null missing-value semanticsCheck constraints and foreign keysOuter joinsAggregate functionsWhen two nulls are equal: grouping, sorting, and some set operationsEffect on index operationNull-handling functionsData typing of Null and UnknownBOOLEAN data typeControversyFurther reading
Videos
GeeksforGeeks
geeksforgeeks.org โบ sql โบ sql-null-values
NULL values in SQL - GeeksforGeeks
May 2, 2017 - CREATE TABLE Employee ( Fname VARCHAR(50), Lname VARCHAR(50), SSN VARCHAR(11), Phoneno VARCHAR(15), Salary FLOAT ); INSERT INTO Employee (Fname, Lname, SSN, Phoneno, Salary) VALUES ('Shubham', 'Thakur', '123-45-6789', '9876543210', 50000.00), ('Aman', 'Chopra', '234-56-7890', NULL, 45000.00), ('Aditya', 'Arpan', NULL, '8765432109', 55000.00), ('Naveen', 'Patnaik', '345-67-8901', NULL, NULL), ('Nishant', 'Jain', '456-78-9012', '7654321098', 60000.00); Select * FROM Employee; ... In this query, it retrieves the Fname and Lname of employees whose SSN is NULL.
Microsoft Learn
learn.microsoft.com โบ en-us โบ dotnet โบ framework โบ data โบ adonet โบ sql โบ handling-null-values
Handling Null Values - ADO.NET | Microsoft Learn
In SQL Server, the ANSI_NULLS option controls both default nullability in the database and evaluation of comparisons against null values. If ANSI_NULLS is turned on (the default), the IS NULL operator must be used in expressions when testing for null values. For example, the following comparison always yields unknown when ANSI_NULLS is on:
Tutorialspoint
tutorialspoint.com โบ home โบ sql โบ sql null values
Understanding SQL NULL Values
November 29, 2009 - Here, NOT NULL signifies that column should always accept an explicit value of the given data type. You can insert NULL values into the columns where we did not use NOT NULL. Let us create a table with the name CUSTOMERS in the SQL database using the CREATE statement as shown in the query below โ
Biztory
biztory.com โบ blog โบ 2019 โบ 07 โบ 22 โบ null-values-tips
7 Things to know about NULL values - Biztory | Biztory
October 25, 2025 - Some people have a nasty tendency to impute the mean or an arbitrary value (e.g. 99, 100, 0, -1) directly into the database. If a value appears suspiciously often or seems impossible; it might be an attempt to input NULL values. ... Just to name a couple of examples: I once saw a database where all of the customers who made a purchase before 2005 had an age of 27.
Essential SQL
essentialsql.com โบ home โบ what is a database null value?
What is a Database NULL Value? - Essential SQL
March 4, 2023 - For instance no two NULL are equal to each other. Surprisingly NULL = NULL is FALSE! SQL covers this dilemma though. You can use the IS NULL and IS NOT NULL comparisons to test for NULL values. For example, the following query from the AdventureWorks2012 database
DbSchema
dbschema.com โบ blog โบ tutorials โบ sql-null-values
SQL NULL Values Explained with Examples
SELECT * FROM table_name WHERE column_name IS NULL; Let's consider a sample database table, Students, as shown below: The SQL query to find the rows where the Age is NULL will be: ... The query selects all rows from the Students table where ...
Navicat
navicat.com โบ en โบ company โบ aboutus โบ blog โบ 1312-the-null-value-and-its-purpose-in-relational-database-systems
The NULL Value and its Purpose in Relational Database Systems
When writing queries, there are times that you'll want to filter out rows with NULL values. Other times, you'll specifically want to retrieve rows that contain NULLs. Here's how to do both: Queries can filter out nulls using the IS NOT NULL clause. Here's an example that excludes films from the Sakila database that contain a NULL original_language_id:
Top answer 1 of 16
80
Nulls are negatively viewed from the perspective of database normalization. The idea being that if a value can be nothing, then you really should split that out into another sparse table such that you don't require rows for items which have no value.
It's an effort to make sure all data is valid and valued.
In some cases having a null field is useful, though, especially when you want to avoid yet another join for performance reasons (although this shouldn't be an issue if the database engine is setup properly, except in extraordinary high performance scenarios.)
2 of 16
46
One argument against nulls is that they don't have a well-defined interpretation. If a field is null, that could be interpreted as any of the following:
- The value is "Nothing" or "Empty set"
- There is no value that makes sense for that field.
- The value is unknown.
- The value hasn't been entered yet.
- The value is an empty string (for databases that don't distinguish between nulls and empty strings).
- Some application-specific meaning (e.g., "If the value is null, then use a default value.")
- An error has occurred, causing the field to have a null value when it really shouldn't.
Some schema designers demand that all values and data types should have well-defined interpretations, therefore nulls are bad.
PREP INSTA
prepinsta.com โบ home โบ dbms (database management system) โบ null values in dbms
Null Values in DBMS | PrepInsta
August 19, 2019 - Special value that is supported ... do not apply for that particular row ยท For example age of a particular student is not available in the age column of student table then it is represented as null but not as zer...
Database Journal
databasejournal.com โบ home โบ features
Working with NULL Values in SQL | DatabaseJournal.com
March 9, 2023 - Here, In this SQL example, we inserted a new employee into the employees table. The phone_number and manager_id columns both contain NULL values. ... If we query data in a relational database that contains NULL values, we must first understand how they are handled in different situations.
Databasedesign-resource
databasedesign-resource.com โบ null-values-in-a-database.html
NULL values in a database
Should we be able to store NULL values in a database. A discussion of NULL values with examples
DataLemur
datalemur.com โบ sql-tutorial โบ sql-null
Handling NULL Values | DataLemur
Health Records: In a patient's medical history, some test results might not be available yet, resulting in NULL values in the test result columns. In essence, values in SQL are like flexible placeholders that cater to the uncertainties and variations in real-world data. They allow databases to accommodate missing or pending information without resorting to assumptions or default values. To demonstrate the usage of SQL functions for handling values, we'll be working with an illustrative table named that contaings details about the best-selling books across diverse genres.
Quora
quora.com โบ What-is-the-definition-of-a-NULL-value-in-a-database-table-Is-it-normal-to-have-a-column-with-a-NULL-value
What is the definition of a NULL value in a database table? Is it normal to have a column with a NULL value? - Quora
Answer (1 of 2): A NULL value in relational database terms represents a value which is not known. It is not zero or space (blank) which are values, simply that the value is unknown. Consider this, lets say we have a database table called โPERSONSโ which contain of the following columns: โLAST_NA...
Khoury College of Computer Sciences
khoury.northeastern.edu โบ home โบ kenb โบ MeaningOfNull.html
The Meaning of Null in Databases and Programming Languages
There are a number of variations on this. Here are a few of them: The value does exist somewhere, but the database does not have it. The value has not yet been determined, but it presumably will be determined at some point. For example, a customer has yet to make a decision about a feature.
Hightouch
hightouch.com โบ sql-dictionary โบ sql-is-null
SQL IS NULL - Syntax, Use Cases, and Examples | Hightouch
December 29, 2023 - The syntax for using the IS NULL operator is as follows: SELECT columns FROM table_name WHERE column_name IS NULL; columns: The columns you want to retrieve in the query. table_name: The name of the table containing the data.
SQL Shack
sqlshack.com โบ working-with-sql-null-values
Working with SQL NULL values
May 19, 2021 - As we stated earlier, SQL Server offers some functions that help to handle NULL values. ISNULL(): The ISNULL() function takes two parameters and it enables us to replace NULL values with a specified value. The expression parameter indicates the expression which we want to check NULL values. The replacement parameter indicates the value which we want to replace the NULL values. For example, in the following query, the ISNULL() function replaces the NULL values in the row with the specified value.
W3Schools
w3schools.com โบ mysql โบ mysql_null_values.asp
MySQL NULL Values - IS NULL and IS NOT NULL
It is not possible to test for NULL values with comparison operators, such as =, <, or <>. We will have to use the IS NULL and IS NOT NULL operators instead. SELECT column_names FROM table_name WHERE column_name IS NULL; SELECT column_names FROM table_name WHERE column_name IS NOT NULL; Below is a selection from the "Customers" table in the Northwind sample database:
Quora
quora.com โบ What-are-some-examples-of-NULL-values-in-SQL-databases
What are some examples of NULL values in SQL databases? - Quora
Answer (1 of 3): The phrase SQL NULL is used to signify a missing value. In a table, a NULL value is a value in a field that seems to be blank. A field with a NULL value is one that has no value. It is critical to realize that a NULL value is not the same as a zero value or a field that contains...