W3Schools
w3schools.com › sql › sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
String Functions: Asc Chr Concat ... Plan SQL Bootcamp SQL Certificate SQL Training ... A field with a NULL value is a field with no value....
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
Reddit
reddit.com › r/learnprogramming › what is null?
r/learnprogramming on Reddit: What is Null?
July 5, 2024 -
So I use C# and I often see many devs use null.
What and which kind of situation do you use this variable?
I am reading c# guide on programming book and I am on Clearing memory now and I haven't encountered null yet. Should I be worried?
Top answer 1 of 20
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This was intended as a meme but is actually a good representation of what "Null" is. In C#, when you declare string s = "My shit"; it means that "s" is a reference to a memory location that holds the data "My shit". string s = null; means that the reference "s" exists but it's not pointing to any object, as in it holds nothing.
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NULL is nothing. It means theres nothing there. Often its just a place holder before something is there. Say u have a bunch of variables of animals. U might set them to NULL before u know what they are. Then u might check if they are NULL before u add an animal to them. Things are initialized as NULL.
DbSchema
dbschema.com › blog › tutorials › sql-null-values
SQL NULL Values Explained with Examples
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.
Navicat
navicat.com › en › company › aboutus › blog › 1312-the-null-value-and-its-purpose-in-relational-database-systems
The NULL Value and its Purpose in Relational Database Systems
This is what is commonly referred to as a "null pointer". In a database, zero is a value which has meaning, so the value NULL became is a special marker to mean that no value exists.
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.
MariaDB
mariadb.com › docs › server › reference › data-types › null-values
NULL Values | Server | MariaDB Documentation
These are all valid values, and are not NULL values. When a table is created or the format altered, columns can be specified as accepting NULL values, or not accepting them, with the NULL and NOT NULL clauses respectively.
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
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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.
Khoury College of Computer Sciences
khoury.northeastern.edu › home › kenb › MeaningOfNull.html
The Meaning of Null in Databases and Programming Languages
When one properly defines database null as the absence of a value, then the strangeness disappears. Another example is his statement, "A weird aspect of nulls is that they are neither equal nor unequal to each other." Once again, the weirdness is due to his misunderstanding, not anything intrinsic.
Microsoft Learn
learn.microsoft.com › en-us › dotnet › framework › data › adonet › sql › handling-null-values
Handling Null Values - ADO.NET | 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).
Esri Support
support.esri.com › en-us › gis-dictionary › null-value
Null Value Definition | GIS Dictionary
The absence of a recorded value for a field. A null value differs from a value of zero in that zero may represent the measure of an attribute, while a null value indicates that no measurement has been
freeCodeCamp
freecodecamp.org › news › a-quick-and-thorough-guide-to-null-what-it-is-and-how-you-should-use-it-d170cea62840
A quick and thorough guide to ‘null’: what it is, and how you should use it
June 12, 2018 - Technically speaking, the memory location assigned to the reference contains the value 0 (all bits at zero), or any other value that denotes null in the given environment. As we learned in the previous section, operations involving null are extremely fast and easy to perform at run-time. ... Initialize or set a reference to null (e.g. name = null): The only thing to do is to change the content of one memory cell (e.g.
Biztory
biztory.com › blog › 2019 › 07 › 22 › null-values-tips
7 Things to know about NULL values - Biztory | Biztory
A NULL value is a special marker used in SQL to indicate that a data value does not exist in the database. In other words, it is just a placeholder to denote values that are missing or that we do not know.
Upwork
upwork.com › resources › articles › {name}
Null in Java: Understanding the Basics - Upwork
August 5, 2024 - In Java, null is a literal, a special constant you can point to whenever you wish to point to the absence of a value.
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › null
null - JavaScript | MDN
JavaScript is unique to have two nullish values: null and undefined. Semantically, their difference is very minor: undefined represents the absence of a value, while null represents the absence of an object.
W3Schools
w3schools.com › mysql › mysql_null_values.asp
MySQL NULL Values - IS NULL and IS NOT NULL
A field with a NULL value is one that has been left blank during record creation!
Safe
docs.safe.com › fme › html › FME-Form-Documentation › FME-Terminology › Confluence-Topics › null__NULL__Null___null_.htm
null, NULL, Null,
An attribute can be null, as can an FME parameter. In both cases, it means that “we don’t know, yet, what value this has.” Any data type can be null, including numeric, string, Boolean, and so forth. Null is not same thing as missing or empty.
MySQL
dev.mysql.com › doc › refman › 8.4 › en › null-values.html
MySQL :: MySQL 8.4 Reference Manual :: 11.1.7 NULL Values
The NULL value means “no data.” NULL can be written in any lettercase.
IBM
ibm.com › docs › en › rbd › 9.6.0
Null values and the nullable type
We cannot provide a description for this page right now
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.