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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 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, ...

special marker and keyword in SQL indicating that something has no value

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 … Wikipedia

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en.wikipedia.org › wiki › Null_(SQL)

Null (SQL) - Wikipedia

1 day ago - The result set generated by this query demonstrates how SQL uses Null as a placeholder for values missing from the right-hand (PhoneNumber) table, as shown below. SQL defines aggregate functions to simplify server-side aggregate calculations on data. Except for the COUNT(*) function, all aggregate functions perform a Null-elimination step, so that Nulls are not included in the final result of the calculation.

History Null propagation Comparisons with NULL and the three-valued logic (3VL)Analysis of SQL Null missing-value semantics Check constraints and foreign keys Outer joins Aggregate functions When two nulls are equal: grouping, sorting, and some set operations Effect on index operation Null-handling functions Data typing of Null and Unknown BOOLEAN data type Controversy Further reading

Videos

How to handle NULL in SQL - YouTube

How To Handle NULL Values In MS SQL Server? - YouTube

September 23, 2024

SQL to find NULL in any column - YouTube

IN clause with NULL values in SQL is broken! #sql - YouTube

Learn SQL: NULL values - YouTube

How to Replace NULL Values in SQL? | SQL Tips and Tricks | Data ...

November 24, 2022

geeksforgeeks.org › sql › sql-null-values

NULL values in SQL - GeeksforGeeks

January 5, 2026 - Since it is often not possible to determine which interpretation applies, SQL treats all NULL values as distinct and does not distinguish between them. Typically, it can have one of three interpretations: Value Unknown: The value exists but is not known. Value Not Available: The value exists but is intentionally withheld. Attribute Not Applicable: The value is undefined for a specific record. Setting a NULL value is appropriate when the actual value is unknown, or when a value is not meaningful.

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

Null values generally indicate data that is unknown, not applicable, or to be added later. For example, a customer's middle initial might not be known at the time the customer places an order.

dbvis.com › thetable › the-definitive-guide-to-the-null-sql-server-value

The Definitive Guide to the NULL SQL Server Value

September 12, 2024 - The NULL SQL Server value acts as a special placeholder to represent the absence of data in a structured and meaningful way.

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

learnsql.com › blog › what-is-null-in-sql

What Is a NULL in SQL? | LearnSQL.com

March 17, 2021 - SQL uses NULLs as a special flag that signals the lack of a value for a field or a variable. NULLs should be used wisely so the database gives a faithful picture of the reality it represents.

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

June 25, 2024 - The ANSI SQL-92 standard does not support columnName = NULL in a WHERE clause. 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.

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stackoverflow.com › questions › 21987177 › what-is-null-in-sql

What is NULL in SQL? - Stack Overflow

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

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.

modern-sql.com › concept › null

Modern SQL: NULL — purpose, comparisons, NULL in expressions, mapping to/from NULL

Expressions and functions that process a null value generally return the null value.4 Noteworthy exceptions are aggregate functions and—due to the three-valued logic of SQL—two logical operations.5 · The result of the following expressions is therefore null: ... The Oracle database treats an empty string as null and vice versa: on the one hand, '' IS NULL is true, on the other hand is null treated as an empty string in string concatenations (||). The Oracle databases returns 'foo bar' for the second example above. SQL Server has the deprecated setting SET CONCAT_NULL_YIELDS_NULL OFF to treat null as an empty string when concatenating strings with the + operator.

sqlshack.com › working-with-sql-null-values

Working with SQL NULL values

May 19, 2021 - The IS NOT NULL condition is used to return the rows that contain non-NULL values in a column. The following query will retrieve the rows from the Person table which are MiddleName column value is not equal to NULL values. As we stated earlier, SQL Server offers some functions that help to handle NULL values.

mssqltips.com › home › sql null meaning and how to handle null values

SQL NULL Meaning and How to Handle NULL Values

June 20, 2024 - This is because the middle string, @String2, remains a NULL value, meaning that any concatenation that includes @String2 will also be NULL. If you’re following along and your demo did NOT do that, there is a reason. There is a connection-level setting that can be changed to tell SQL Server to treat NULL values like empty strings when doing concatenation.

medium.com › @riat06 › behaviour-of-null-values-in-sql-48c18564c46

Behaviour of NULL values in SQL. How does null value affects different… | by Ria Thomas | Medium

August 30, 2024 - So, this is a short article to list down the main operations in SQL and how NULL values affect them. ... Before getting into how to handle NULL values, it’s important to understand what qualifies as NULL. NULL does not mean an empty string or spaces or zeros.

Microsoft Learn

learn.microsoft.com › en-us › dotnet › framework › data › adonet › sql › handling-null-values

Handling Null Values - ADO.NET | Microsoft Learn

September 15, 2021 - The ANSI SQL-92 standard does not support columnName = NULL in a WHERE clause. 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 ...

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 ...

4js.com › online_documentation › fjs-fgl-manual-html › fgl-topics › c_fgl_sql_programming_nulls.html

Genero Business Development Language - The NULL value

The SQL concept of NULL means "no value" or "undefined value". This is used in SQL to insert or update table rows and omit values for some fields that are not mandatory.

dbvis.com › thetable › dealing-with-null-in-sql-complete-guide

Dealing With NULL in SQL: Complete Guide

April 9, 2025 - In SQL, NULL represents missing or unknown values in a database table. Unlike zero or an empty string, NULL signifies the absence of a value–not zero, not an empty string, but a true unknown or undefined value.

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 ...

geeksforgeeks.org › sql › sql-select-null

SQL - SELECT NULL - GeeksforGeeks

July 23, 2025 - In SQL, the term NULL represents a missing or undefined value in a table. A NULL value is different from a zero or an empty string; it signifies that no data exists for that field.

Database Journal

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Working with NULL Values in SQL | DatabaseJournal.com

March 9, 2023 - In relational databases and RDBMS’, NULL values are a special value in SQL that are used to represent an unknown – or in some instances, a missing – value in a column or cell.