W3Schools
w3schools.com › sql › sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this field.
special marker and keyword in SQL indicating that something has no value
Factsheet
Null (SQL)
Notation ω
Null (SQL)
Notation ω
Wikipedia
en.wikipedia.org › wiki › Null_(SQL)
Null (SQL) - Wikipedia
1 week ago - NULL is a special marker used to indicate that a data value does not exist in the database. Introduced by the creator of the relational database model, E. F. Codd, SQL null serves to fulfill the requirement that all true relational database management systems (RDBMS) support a representation ...
Videos
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SQL Tutorial #17 - SQL IS NULL and IS NOT NULL | SQL NULL Values ...
SQL SERVER : Working With Null Value
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Different ways to replace NULL in sql server - Part 15 - YouTube
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Understanding NULL Values in SQL | What NULL Means and How to Use ...
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10 NULL values in SQL : How to identify and handle them ? - YouTube
11:18
Working with SQL NULL values | Null Handling Functions - YouTube
Tutorialspoint
tutorialspoint.com › sql › sql-null-values.htm
SQL - NULL Values
SQL uses the term NULL to represent a non-existent data value in the database. These values are not the same as an empty string or a zero. They don't hold any space in the database and are used to signify the absence of a value or the unknown value in a data field.
DbSchema
dbschema.com › blog › tutorials › sql-null-values
SQL NULL Values Explained with Examples
It is a distinct concept that represents missing or unknown data. In other words, NULL signifies the absence of any value. The IS NULL operator in SQL is used to check whether a column value is NULL or not.
Microsoft Learn
learn.microsoft.com › en-us › sql › t-sql › language-elements › null-and-unknown-transact-sql
NULL and UNKNOWN (Transact-SQL) - SQL Server | Microsoft Learn
Comparisons between two null values, or between a null value and any other value, return unknown because the value of each NULL is unknown. Null values generally indicate data that is unknown, not applicable, or to be added later.
GeeksforGeeks
geeksforgeeks.org › sql › sql-null-values
NULL values in SQL - GeeksforGeeks
July 23, 2025 - In SQL, some records in a table may not have values for every field, and such fields are termed as NULL values. These occur when data is unavailable during entry or when the attribute does not apply to a specific record.
LearnSQL.com
learnsql.com › blog › what-is-null-in-sql
What Is a NULL in SQL? | LearnSQL.com
An SQL NULL value is a flag that signals the lack of a value for a data field. Learn how to work with it in SQL queries.
Microsoft Learn
learn.microsoft.com › en-us › sql › connect › ado-net › sql › handle-null-values
Handling null values - ADO.NET Provider for SQL Server | Microsoft Learn
A null value in a relational database is used when the value in a column is unknown or missing. A null is neither an empty string (for character or datetime data types) nor a zero value (for numeric data types).
Scaler
scaler.com › topics › sql › null-value-in-sql
NULL Value in SQL - Scaler Topics
April 20, 2022 - NULL in SQL represents a column field in the table with no value. NULL is different from a zero value and from "none". NULL can be inserted in any column by using the assignment operator "=". Also, to test whether a NULL is present or not we ...
SQL Shack
sqlshack.com › working-with-sql-null-values
Working with SQL NULL values
May 19, 2021 - This article will explain what problems can occur when working with SQL NULL values and it also gives some solution recommendations to overcome these issues. In terms of the relational database model, a NULL value indicates an unknown value.
DataLemur
datalemur.com › sql-tutorial › sql-null
Handling NULL Values | DataLemur
In SQL, indicates the absence of a value. Unlike an empty string or zero, doesn't represent a specific value, but rather, a missing or unknown piece of information. Here's an overview of what you'll learn in this tutorial: ... Handling NULL ...
DB Vis
dbvis.com › thetable › the-definitive-guide-to-the-null-sql-server-value
The Definitive Guide to the NULL SQL Server Value
September 12, 2024 - Read this article to ensure that your knowledge of NULL values is not null! In SQL Server, NULL indicates data that is unknown, not applicable, or yet to be provided. For example, assume a column for a middle name is nullable.
ThoughtSpot
thoughtspot.com › sql-tutorial › sql-is-null
SQL IS NULL | Basic SQL | ThoughtSpot
3 weeks ago - IS NULL is a logical operator in SQL that allows you to exclude rows with missing data from your results. Some tables contain null values—cells with no data in them at all. This can be confusing for heavy Excel users, because the difference ...
Top answer 1 of 5
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In simple worlds you can say that Null is not a data value, but a marker for an unknown value.
So any mathematical operations performed on NULL will result in NULL. For example,
10 + NULL = NULL
Similarly if you do string concatenation with string you get:-
'String ' || NULL || 'Concatenation' -- Result is NULL
So you can say that Null means either "not applicable" or "don't know": it is not the same as zero (0) or any other default value, but more importantly, null is treated quite differently from other values in SQL, because it literally has no value.
An example to explain what it means when we say that NULL means UNKNOWN VALUE:
StudentName TestResult
X 78
A 89
B 67
C NULL
So you can see that the student C got NULL marks in the test. So what does that mean?
Now one can say that the student does not sit in the test or it may be that the student's data is not avaialable. But it definitely does not mean that the student got 0(as if you assign 0 to the student then it would mean that the student appeared in the test and got zero) marks in the test. All we can say that the data for the student is
UNKNOWN or NULL
2 of 5
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A field with a NULL value is a field with no value. It is very important to understand that a NULL value is different than a zero value or a field that contains spaces.
If a column in a table is optional, we can insert a new record or update an existing record without adding a value to this column. This means that the field will be saved with a NULL value.
NULL values are treated differently from other values.
NULL is used as a placeholder for unknown or inapplicable values. Read more about this here.
W3Schools
w3schools.com › sql › sql_ref_is_null.asp
SQL IS NULL
The IS NULL command is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field:
Codedamn
codedamn.com › news › sql
NULL Values in SQL
May 18, 2023 - In SQL, NULL signifies the absence of information or a missing value. This is different from a zero value or a field that contains spaces. A NULL value is a field with no value; it is not equivalent to zero or a space, which are actual values.
Essential SQL
essentialsql.com › home › what is a database null value?
What is a Database NULL Value? - Essential SQL
March 4, 2023 - In SQL, this is solved with null. It is used to signify missing or unknown values. The keyword NULL is used to indicate these values. NULL really isn’t a specific value as much as it is an indicator.
Modern SQL
modern-sql.com › concept › null
Modern SQL: NULL — purpose, comparisons, NULL in expressions, mapping to/from NULL
SQL uses two different concepts to tell if two values are the “same”: equals (=) and distinct. The difference is that equals (=) treats comparisons to null as indeterminate—that’s why col = null returns unknown. Distinct, on the other hand, treats null like any other value—i.e.
Microsoft Learn
learn.microsoft.com › en-us › sql › t-sql › queries › is-null-transact-sql
IS NULL (Transact-SQL) - SQL Server | Microsoft Learn
If the value of expression is NULL, IS NOT NULL returns FALSE; otherwise, it returns TRUE. To determine whether an expression is NULL, use IS NULL or IS NOT NULL instead of comparison operators (such as = or !=). Comparison operators return UNKNOWN when either or both arguments are NULL. The code samples in this article use the AdventureWorks2025 or AdventureWorksDW2025 sample database, which you can download from the Microsoft SQL Server Samples and Community Projects home page.
Oracle
docs.oracle.com › en › database › oracle › oracle-database › 19 › sqlrf › Nulls.html
SQL Language Reference
September 24, 2025 - If a column in a row has no value, then the column is said to be null, or to contain null. Nulls can appear in columns of any data type that are not restricted by NOT NULL or PRIMARY KEY integrity constraints.