Microsoft Learn
learn.microsoft.com โบ en-us โบ sql โบ t-sql โบ language-elements โบ 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.
W3Schools
w3schools.com โบ sql โบ sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
Below is a selection from the Customers table used in the examples: The IS NULL operator is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field:
Videos
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SQL NULL vs Empty String vs Blank Space (Visually Explained) | ...
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SQL | Null Function in SQL | ISNULL | COALESCE | IFNULL | NVL - ...
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SQL Tutorial #17 - SQL IS NULL and IS NOT NULL | SQL NULL Values ...
01:03:16
How to handle NULL in SQL - YouTube
02:07
SQL query to check IS Null and IS not Null data - YouTube
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 - 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 ...
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
Baeldung
baeldung.com โบ home โบ sql queries โบ find null or empty values in sql
Find Null or Empty Values in SQL Baeldung on SQL
August 20, 2025 - NULL values in SQL represent missing or unknown data in a database column. This can occur for two reasons: the data does not exist, or it exists but is currently unknown. In contrast, an empty value, such as an empty string, is a specific value ...
GeeksforGeeks
geeksforgeeks.org โบ sql โบ sql-null-values
NULL values in SQL - GeeksforGeeks
May 2, 2017 - 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.
DB Vis
dbvis.com โบ thetable โบ 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.
Coginiti
coginiti.co โบ home โบ beginner โบ sql is null
What is the IS NULL Operator in SQL? - Coginiti
September 25, 2023 - A NULL value indicates that the data is missing or unknown, while a value of 0 indicates that the data is explicitly known and set to zero. If you are analyzing a stock table, the quantity of a product would be NULL when you donโt have the ...
LearnSQL.com
learnsql.com โบ blog โบ 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.
DbSchema
dbschema.com โบ blog โบ tutorials โบ sql-null-values
SQL NULL Values Explained with Examples
In SQL, NULL is a special marker used to indicate that a data value does not exist in the database. It is important to note that NULL is not the same as an empty string or a zero value.
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
2
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.
ThoughtSpot
thoughtspot.com โบ sql-tutorial โบ sql-is-null
SQL IS NULL | Basic SQL | ThoughtSpot
November 18, 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.
Reddit
reddit.com โบ r/learnsql โบ what is a null in sql? is it the same as a empty cell?
r/learnSQL on Reddit: What is a null in sql? is it the same as a empty cell?
October 5, 2022 -
Lets say i have a Excel sheet , col : name and ID . some rows cells in "name" are empty in datasheet.
now sql pulls this data, will the empty cells be filled with a null value by default?
or is null a unique type of character that is only used to overwrite existing values , so when system reads it it thinks its empty?
Top answer 1 of 5
12
NULL, in simplest terms, is the absence of data. Not to be confused with '', an empty string. If you are familiar with other languages, you could think of it as similar to undefined, in that the column has a type defined, but the specific cell has no data, and is more of a place holder for future data. When filtering for NULL, you will need to do things like table.col is null or table.col is not null In your Excel example, it depends on how you import the data, and what the definition of the target table is. The target table may have rules built into it to default the data for certain columns, or reject NULL values from other columns. You could have Null, an empty string, zero, weird dates.. etc.
2 of 5
3
NULL Is not equal to empty cell. Empty cells can sometimes contain space in the cell and you'll not be able to filter these out with NULL For Empty cells you could use LEN() in Excel.
Mimo
mimo.org โบ glossary โบ sql โบ 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.
Tutorialspoint
tutorialspoint.com โบ home โบ sql โบ sql null values
Understanding SQL NULL Values
November 29, 2009 - 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 ...
Scaler
scaler.com โบ home โบ topics โบ sql โบ 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.
Hightouch
hightouch.com โบ sql-dictionary โบ 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 ...
Modern SQL
modern-sql.com โบ concept โบ null
Modern SQL: NULL โ purpose, comparisons, NULL in expressions, mapping to/from NULL
The null value does not indicate why a value is absentโit 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.
W3Schools
w3schools.com โบ mysql โบ mysql_null_values.asp
MySQL NULL Values - IS NULL and IS NOT NULL
Below is a selection from the "Customers" table in the Northwind sample database: The IS NULL operator is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field:
GeeksforGeeks
geeksforgeeks.org โบ sql โบ sql-is-null-operator
SQL IS NULL Operator - GeeksforGeeks
December 31, 2023 - The SQL IS NULL operator checks whether a column contains a NULL (missing or unknown) value. Since NULL is not the same as zero or an empty string, IS NULL is used in the WHERE clause to filter rows where a value is absent.
SQLTeam
forums.sqlteam.com โบ t โบ is-null-vs-null โบ 21223
IS NULL vs =NULL - SQLTeam.com Forums
June 15, 2022 - How can the below return different things ยท NULL is an unknown value and therefore a NULL value can never be equal to another value, even if that other value is NULL. NULL = NULL is unknown and cannot be true - eliminating that row from the ...