W3Schools
w3schools.com › sql › 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 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 ...
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
July 20, 2026 - 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.
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SQL short ISNULL. What is ISNULL and how does it work. - YouTube
SQL Tutorial: How to Use and Handle NULL Values? - YouTube
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SQL - NULL Values - W3Schools.com - YouTube
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Learn about NULL values in SQL - learn SQL pt 8 - YouTube
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SQL query to check IS Null and IS not Null data - YouTube
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IS NULL Operator in SQL | SQL Tutorial - YouTube
What is the difference between a null cell and an empty cell in SQL?
A null cell contains no data, while an empty or space-filled cell holds an actual value that just looks blank. Unlike Excel, SQL treats these two cases differently, so a space-filled cell won't match IS NULL. To catch both, combine IS NULL with a check like TRIM(column) = ''.
thoughtspot.com
thoughtspot.com › sql-tutorial › sql-is-null
SQL IS NULL | Basic SQL | ThoughtSpot
Why doesn't WHERE column = NULL work?
"WHERE column = NULL" doesn't work because you can't run a comparison or arithmetic against a null value. Since null represents the absence of data, SQL has nothing to compare against, so the condition never returns true. Use "IS NULL" instead, which is built for this exact check.
thoughtspot.com
thoughtspot.com › sql-tutorial › sql-is-null
SQL IS NULL | Basic SQL | ThoughtSpot
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
July 24, 2026 - In the SQL database query language, null or 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 ...
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
GeeksforGeeks
geeksforgeeks.org › sql › sql-null-values
NULL values in SQL - GeeksforGeeks
January 5, 2026 - A NULL value is not equivalent to a value of ZERO if the data type is a number and is not equivalent to spaces if the data type is a character. A NULL value can be inserted into columns of any data type. A NULL value will evaluate NULL in any expression. Suppose if any column has a NULL value, then UNIQUE, FOREIGN key, and CHECK constraints will ignore by SQL.
Hightouch
hightouch.com › sql-dictionary › sql-is-null
SQL IS NULL - Syntax, Use Cases, and Examples | Hightouch
December 29, 2023 - The SQL IS NULL operator is used to filter rows where a specified column's value is NULL. A NULL value in a database represents the absence of data, and the IS NULL operator is used to identify and select rows that contain NULL values in a ...
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.
LearnSQL.com
learnsql.com › blog › what-is-null-in-sql
What Is a NULL in SQL? | LearnSQL.com
March 17, 2021 - Simply put, an SQL NULL means that we don’t have a value for that particular field. Maybe we don’t know what the value will be and we need a placeholder, like when an order has been shipped to a customer but not delivered yet; in that case, the delivery date will be NULL until the order has arrived. Or maybe there’s an attribute that is true for some people and not others, e.g.
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 ...
ThoughtSpot
thoughtspot.com › sql-tutorial › sql-is-null
SQL IS NULL | Basic SQL | ThoughtSpot
November 5, 2025 - Starting here? This lesson is part of a full-length tutorial in using SQL for Data Analysis. Check out the beginning. ... IS NULL is a logical operator in SQL that allows you to exclude rows with missing data from your results.
Mimo
mimo.org › glossary › sql › is-null
SQL IS NULL Condition: Syntax, Usage, and Examples
The SQL IS NULL condition helps you check if a column contains no value, meaning it's undefined or missing. In relational databases, NULL represents the absence of data, not zero or an empty string.
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.
Modern SQL
modern-sql.com › concept › null
Modern SQL: NULL — purpose, comparisons, NULL in expressions, mapping to/from NULL
The null value does not indicate why a value is absent—it simply marks the places that do not have a data value. For example, the SQL language itself uses the null value for the absent values resulting from an outer join.2 Although exceptions exist,3 it is not generally possible to tell why a value is null.
Scaler
scaler.com › home › topics › sql › null value in sql
NULL Value in SQL - Scaler Topics
March 28, 2024 - NULL value in SQL signifies that the column's corresponding value is either undefined or unknown.
MSSQLTips
mssqltips.com › home › sql null meaning and how to handle null values
SQL NULL Meaning and How to Handle NULL Values
June 20, 2024 - It will then show how these values can make queries act unexpectedly and how to best interact with NULL values to avoid problems. NULL isn’t a value but rather the absence of a value.
Medium
medium.com › @tw4512 › working-with-null-in-sql-a-beginners-guide-12-6a1a6948c622
Working with Null in SQL: A Beginner’s Guide(12) | by Tamanna shaikh | Medium
February 16, 2024 - They represent the absence or unknown of any data in a column. In this blog post, we will learn how to handle null values in SQL queries using various techniques and functions. This is part of our SQL Learning series, where we cover the basics ...
Enki
enki.com › post › understanding-null-values-in-sql
Enki | Blog - Understanding NULL Values in SQL
Unlike a zero value, which indicates a known absence, or an empty string, which represents a present but empty value, NULL signifies the absence of any data value. Proper handling of NULL values is crucial when performing various database operations such as comparisons, sorting, and aggregations.
W3Schools
w3schools.com › sql › sql_ref_is_null.asp
SQL IS NULL
String Functions: Asc Chr Concat ... SQL Study Plan SQL Bootcamp SQL Training ... The IS NULL command is used to test for empty values (NULL values)....
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.
Oracle
docs.oracle.com › en › database › oracle › oracle-database › 26 › sqlrf › Nulls.html
Nulls
1 week ago - 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.
GeeksforGeeks
geeksforgeeks.org › sql › sql-is-null-operator
SQL IS NULL Operator - GeeksforGeeks
The SQL IS NULL operator checks whether a column contains a NULL (missing or unknown) value.
Published: 3 weeks ago