<> is Standard SQL-92; != is its equivalent. Both evaluate for values, which NULL is not -- NULL is a placeholder to say there is the absence of a value.
Which is why you can only use IS NULL/IS NOT NULL as predicates for such situations.
This behavior is not specific to SQL Server. All standards-compliant SQL dialects work the same way.
Note: To compare if your value is not null, you use IS NOT NULL, while to compare with not null value, you use <> 'YOUR_VALUE'. I can't say if my value equals or not equals to NULL, but I can say if my value is NULL or NOT NULL. I can compare if my value is something other than NULL.
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<> is Standard SQL-92; != is its equivalent. Both evaluate for values, which NULL is not -- NULL is a placeholder to say there is the absence of a value.
Which is why you can only use IS NULL/IS NOT NULL as predicates for such situations.
This behavior is not specific to SQL Server. All standards-compliant SQL dialects work the same way.
Note: To compare if your value is not null, you use IS NOT NULL, while to compare with not null value, you use <> 'YOUR_VALUE'. I can't say if my value equals or not equals to NULL, but I can say if my value is NULL or NOT NULL. I can compare if my value is something other than NULL.
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NULL has no value, and so cannot be compared using the scalar value operators.
In other words, no value can ever be equal to (or not equal to) NULL because NULL has no value.
Hence, SQL has special IS NULL and IS NOT NULL predicates for dealing with NULL.
W3Schools
w3schools.com › sql › sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
SELECT column_names FROM table_name WHERE column_name 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:
sql if value is null not equal does not work
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Download Microsoft Edge More info about Internet Explorer and Microsoft Edge ... I have the below query, but the AND pd.FROMLOC <> 'DMS' does not work if the column has {null} is there ... More on learn.microsoft.com
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August 18, 2020Need some knowledge on NULL and NOT NULL
a null is used for multiple purposes -- for example, not known, not applicable, etc. theoreticians take great joy in debating which uses are valid, and whether they can be substituted by some non-null placeholder suffice to say, a null is used when you don't know what value should go there if you don't want that situation to arise, just make the column NOT NULL and you'll never be able to not insert an actual value More on reddit.com
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December 22, 2021sql if value is null not equal does not work - Oracle Forums
For appeals, questions and feedback about Oracle Forums, please email [email protected]. Technical questions should be asked in the appropriate category. Thank you · I have the below query, but the AND pd.FROMLOC <> 'DMS' does not work if the column has {null} is there ... More on forums.oracle.com
I think I'm being an idiot. My dev submitted some SQL with an OR clause, but it's working like an AND clause. What am I missing? I might need an ELI5 since I suspect I am being very dumb.
try changing the (l_name != NULL AND f_name != NULL) into (l_name IS NOT NULL AND f_name IS NOT NULL) Additional reference, https://stackoverflow.com/questions/3059805/difference-between-mysql-is-not-null-and More on reddit.com
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May 22, 2019Videos
06:54
SQL Tutorial #17 - SQL IS NULL and IS NOT NULL | SQL NULL Values ...
11:19
SQL - Part 40 - Null Value, Is Null Operator and Is Not Null Operator ...
SQL IS NULL / IS NOT NULL Operator | NULL values in SQL ...
02:44
SQL Tutorial for Data Analysis 13: IS NULL Operator - YouTube
11:18
Working with SQL NULL values | Null Handling Functions - YouTube
05:38
Solving SQL Issues with Select Where Not Exists with Nulls - YouTube
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Consider checking documentation:
NULL indicates that the value is unknown. A null value is different from an empty or zero value. No two null values are equal. Comparisons between two null values, or between a null value and any other value, return unknown because the value of each NULL is unknown.
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If you consider that the value of istrue is unknown in the NULL case then it might or might not equal 1.
The expression istrue != 1 then evaluates to unknown
SQL only returns rows where the WHERE clause evaluates to true.
If you are on SQL Server 2022+ you can use
WHERE istrue IS DISTINCT FROM 1
To give the inequality semantics that you want (Fiddle).
Quora
quora.com › How-do-you-write-not-equal-to-null-in-an-SQL-query
How to write not equal to null in an SQL query - Quora
Answer: A comparison with NULL using the normal comparison operators will always return false, i.e. [code ]NULL = NULL[/code] is false in SQL. To account for this we use the special [code ]IS[/code] and [code ]IS NOT[/code] operators to check ...
W3Schools
w3schools.com › mysql › mysql_null_values.asp
MySQL NULL Values - IS NULL and IS NOT NULL
SELECT column_names FROM table_name WHERE column_name 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:
Oracle
docs.oracle.com › en › database › other-databases › nosql-database › 25.1 › sqlreferencefornosql › is-null-and-is-not-null-operators.html
IS NULL and IS NOT NULL Operators
April 28, 2025 - If the input expression returns ... returns true if and only if the single item computed by the input expression is NULL. The IS NOT NULL operator is equivalent to NOT (IS NULL cond_expr)....
Microsoft Learn
learn.microsoft.com › en-us › answers › questions › 69728 › sql-if-value-is-null-not-equal-does-not-work
sql if value is null not equal does not work - Microsoft Q&A
August 18, 2020 - I have the below query, but the AND pd.FROMLOC <> 'DMS' does not work if the column has {null} is there a workaround? SELECT pd.wavekey, pd.orderkey, o.externorderkey, pd.pickdetailkey, pd.status, pd.fromloc, pd.loc, pd.sku, pd.qty,…
Reddit
reddit.com › r/sql › need some knowledge on null and not null
r/SQL on Reddit: Need some knowledge on NULL and NOT NULL
December 22, 2021 -
Where and why exactly a null is used?
What is exactly null and not null? To my understanding Not null we use when its mandatory to insert some value in that field, also when we give check constraint so by default the column will be not null right?
By adding new column through alter method default values are null, so how would I be able to insert values in it and is it right to give not null constraint to that new column while adding through alter method, basically when null and when not null to be used?...
god this is so confusing please help me, ik im asking alot but im really confused
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a null is used for multiple purposes -- for example, not known, not applicable, etc. theoreticians take great joy in debating which uses are valid, and whether they can be substituted by some non-null placeholder suffice to say, a null is used when you don't know what value should go there if you don't want that situation to arise, just make the column NOT NULL and you'll never be able to not insert an actual value
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Thoughts in this can vary but I'll give my input. NULL should be used where it is known that there can definitely be no value. If a person's record has an optional telephone number when signing up to a website, and they do not complete a number upon their submission, then a NULL is a valid value. However, if we are utilising something like "effective from" and "effective to" of a row of data, then effective to should never be NULL, we always determine that a row is either currently effective, or is historic and superceded. As a result, the "active" row should not hold a NULL in effective to, even though it is not known. It should be a future, default date, and the column should be set with a NOT NULL constraint.
MariaDB
mariadb.com › docs › server › reference › sql-structure › operators › comparison-operators › not-equal
!= | Server | MariaDB Documentation
What is this page about?What should I read next?Can you give an example? ... Not equal operator. Evaluates both SQL expressions and returns 1 if they are not equal, and 0 if they are equal, or NULL if either expression is NULL.
Hightouch
hightouch.com › sql-dictionary › sql-is-not-null
SQL IS NOT NULL - Syntax, Use Cases, and Examples | Hightouch
December 29, 2023 - The SQL IS NOT NULL operator is used to filter rows in a database table where a specified column's value is not NULL. It is the opposite of the IS NULL operator.
DataCamp
datacamp.com › tutorial › sql-not-equal
SQL NOT EQUAL Operator: A Beginner's Guide | DataCamp
December 10, 2024 - It is commonly used to retrieve ... as it aligns with ISO standards, making queries more universally interpretable. No, the NOT EQUAL operator does not handle NULL values directly....
DB Vis
dbvis.com › thetable › sql-not-equal-operator-definitive-guide-with-examples
SQL Not Equal Operator: Definitive Guide with Examples
October 14, 2024 - In other words, the non-standard syntax for the SQL not equal comparison operator is: ... Note that if any of the two expressions is NULL, the result of the not equal comparison is NULL.
Microsoft Learn
learn.microsoft.com › en-us › sql › t-sql › queries › is-null-transact-sql
IS NULL (Transact-SQL) - SQL Server | Microsoft Learn
3 weeks ago - ... If the value of expression is NULL, IS NULL returns TRUE; otherwise, it returns FALSE. If the value of expression is NULL, IS NOT NULL returns FALSE; otherwise, it returns TRUE.
W3Schools
w3schools.com › sql › sql_isnull.asp
W3Schools.com
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Wikipedia
en.wikipedia.org › wiki › Null_(SQL)
Null (SQL) - Wikipedia
1 week ago - This is not an Unknown value, it is a Null representing the absence of a value. The result would be: Because SQL:2003 defines all Null markers as being unequal to one another, a special definition was required in order to group Nulls together when performing certain operations. SQL defines "any two values that are equal to one another, or any two Nulls", as "not distinct".
Simplilearn
simplilearn.com › home › resources › software development › sql not equal to operator - syntax & examples
SQL Not Equal To Operator - Syntax & Examples
September 9, 2025 - Learn about the
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Oracle
forums.oracle.com › ords › apexds › post › sql-if-value-is-null-not-equal-does-not-work-4157
sql if value is null not equal does not work - Oracle Forums
August 18, 2020 - I have the below query, but the AND pd.FROMLOC 'DMS' does not work if the column has {null} is there a workaround? SELECT pd.wavekey, pd.orderkey, o.externorderkey, pd.pickdetailkey...
Microsoft Learn
learn.microsoft.com › en-us › sql › t-sql › language-elements › not-equal-to-transact-sql-exclamation
!= (Not Equal To) (Transact-SQL) - SQL Server | Microsoft Learn
3 weeks ago - Applies to: SQL Server Azure SQL ... is not equal to another expression (a comparison operator). If either or both operands are NULL, NULL is returned....
W3Schools
w3schools.com › sql › sql_not.asp
SQL NOT Operator
ADD ADD CONSTRAINT ALL ALTER ALTER COLUMN ALTER TABLE AND ANY AS ASC BACKUP DATABASE BETWEEN CASE CHECK COLUMN CONSTRAINT CREATE CREATE DATABASE CREATE INDEX CREATE OR REPLACE VIEW CREATE TABLE CREATE PROCEDURE CREATE UNIQUE INDEX CREATE VIEW DATABASE DEFAULT DELETE DESC DISTINCT DROP DROP COLUMN DROP CONSTRAINT DROP DATABASE DROP DEFAULT DROP INDEX DROP TABLE DROP VIEW EXEC EXISTS FOREIGN KEY FROM FULL OUTER JOIN GROUP BY HAVING IN INDEX INNER JOIN INSERT INTO INSERT INTO SELECT IS NULL IS NOT NULL JOIN LEFT JOIN LIKE LIMIT NOT NOT NULL OR ORDER BY OUTER JOIN PRIMARY KEY PROCEDURE RIGHT JOIN ROWNUM SELECT SELECT DISTINCT SELECT INTO SELECT TOP SET TABLE TOP TRUNCATE TABLE UNION UNION ALL UNIQUE UPDATE VALUES VIEW WHERE MySQL Functions
Coginiti
coginiti.co › home › analysis › compare values when one is null
How to Compare Two Values in SQL When One Is Null - Coginiti
February 1, 2024 - When one value is null in SQL, you cannot directly compare it to any other value using comparison operators such as “=”. Instead, you need to use the IS NULL or IS NOT NULL operator to check whether a value is null.