W3Schools
w3schools.com › sql › sql_notnull.asp
SQL NOT NULL Constraint
To define a NOT NULL constraint when creating a table, add NOT NULL after the data type of the column name. The following SQL creates a "Persons" table, and ensures that the "ID", "LastName", and "FirstName" columns cannot accept NULL values:
GeeksforGeeks
geeksforgeeks.org › sql › sql-not-null-constraint
SQL NOT NULL Constraint - GeeksforGeeks
February 10, 2026 - In SQL, NOT NULL constraint in SQL ensures a column must always contain a value and cannot be left empty.
Videos
SQL Tutorial #12 Constraints in SQL | Usage of NOT NULL ...
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MySQL: NOT NULL constraint - YouTube
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SQL NOT NULL CONSTRAINT - YouTube
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6. NOT NULL & UNIQUE CONSTRAINTS | sql tutorial - YouTube
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14. What is Not Null Constraint in SQL Server | Properties | SQL ...
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14 Not null constraint in sql server - YouTube
Tutorialspoint
tutorialspoint.com › sql › sql-not-null-constraint.htm
SQL - NOT NULL Constraint
The NOT NULL constraint in SQL ensures that a column cannot contain NULL (empty) values. It inserting or updating a row with NULL in that column. By default, if no value is provided for a column when inserting data, SQL assigns it a NULL value.
Programiz
programiz.com › sql › not-null
SQL NOT NULL Constraint (With Examples)
In SQL, the NOT NULL constraint in a column means that the column cannot store NULL values. In this tutorial, you will learn about the SQL NOT NULL constraint with the help of examples.
PopSQL
popsql.com › learn-sql › sql-server › how-to-add-a-not-null-constraint-in-sql-server
How to Add a NOT NULL Constraint in SQL Server
Learn how to add a NOT NULL constraint in SQL Server for a specific column. Use the "ALTER TABLE" command with "ALTER COLUMN" and specify the "NOT NULL" attribute in the column definition to enforce data validation.
W3Schools
w3schools.com › mysql › mysql_notnull.asp
MySQL NOT NULL Constraint
To define a NOT NULL constraint when creating a table, add NOT NULL after the data type of the column name. The following SQL creates a "Persons" table, and ensures that the "ID", "LastName", and "FirstName" columns cannot accept NULL values:
CockroachDB Docs
cockroachlabs.com › docs › stable › not-null
NOT NULL constraint
The NOT NULL constraint specifies a column may not contain NULL values. INSERT or UPDATE statements containing NULL values are rejected.
LearnSQL.com
learnsql.com › blog › not-null-constraint-sql
What Is a NOT NULL Constraint in SQL? | LearnSQL.com
In this article, we will cover the NOT NULL constraint, which is used to avoid having NULL values in a column. Remember, a NULL value in a column represents the absence of a defined value.
Hightouch
hightouch.com › sql-dictionary › sql-not-null
SQL NOT NULL - Syntax, Use Cases, and Examples | Hightouch
December 29, 2023 - A NOT NULL constraint in SQL is a database constraint that ensures a column must always contain a value. It prohibits the insertion of NULL values, making it mandatory for every row to have a non-null value in the specified column.
SQLite Tutorial
sqlitetutorial.net › home › sqlite not null constraint
SQLite NOT NULL Constraint
April 3, 2022 - By default, all columns in a table accept NULL values except you explicitly use NOT NULL constraints. To define a NOT NULL constraint for a column, you use the following syntax: CREATE TABLE table_name ( ..., column_name type_name NOT NULL, ... ); Code language: SQL (Structured Query Language) (sql)
CastorDoc
castordoc.com › how-to › how-to-add-a-not-null-constraint-in-sql-server
How to Add a NOT NULL Constraint in SQL Server?
It defines a rule that specifies that a column must have a value and cannot be left empty. By enforcing this constraint, you can ensure that critical information is always available, preventing inconsistencies and errors in your data.
SQL Tutorial
sqltutorial.org › home › sql not null constraint
SQL NOT NULL Constraint
January 24, 2025 - The NOT NULL constraint prevents inserting or updating NULL into a specified column. It is helpful for defining important columns that should never be NULL. To apply a NOT NULL constraint to a column, you use the following syntax: column_name datatype NOT NULLCode language: SQL (Structured ...
SQL Shack
sqlshack.com › commonly-used-sql-server-constraints-not-null-unique-primary-key
Constraints in SQL Server: SQL NOT NULL, UNIQUE and SQL PRIMARY KEY
June 16, 2021 - By default, the columns are able to hold NULL values. A NOT NULL constraint in SQL is used to prevent inserting NULL values into the specified column, considering it as a not accepted value for that column.
Top answer 1 of 4
3
No sql server considers a NULL to be NULL. If you want to prevent a NULL from being inserted then make the column NOT NULL. Any type of equality check against a NULL value will always return NULL. It can't be greater than 0, less than 0 or equals 0 because the value is unknown.
2 of 4
1
Good catch man! but check constraint works that way, read along.
The CHECK constraints reject values that cause the Boolean expression evaluates to FALSE. Because NULL evaluates to UNKNOWN, it can be used in the expression to bypass a constraint.
For example, you can insert a product whose unit price is NULL as shown in the following query:
INSERT INTO test.products(product_name, unit_price)
VALUES ('Another Awesome Bike', NULL);
NULL is not a really value but it indicates missing tuple value.
Please try read NULL here.
Source: http://www.sqlservertutorial.net/sql-server-basics/sql-server-check-constraint/#targetText=SQL%20Server%20CHECK%20constraint%20and,expression%20to%20bypass%20a%20constraint.&targetText=SQL%20Server%20inserted%20NULL%20into,did%20not%20return%20an%20error.
See this stackoverflow answer as well.
W3Schools
w3schools.com › sql › sql_ref_not_null.asp
SQL NOT NULL
String Functions: Asc Chr Concat ... SQL Bootcamp SQL Certificate SQL Training ... The NOT NULL constraint enforces a column to not accept NULL values, which means that you cannot insert or update a record without adding a value ...
SQL Server Tutorial
sqlservertutorial.net › home › sql server basics › sql server not null constraint
Essential Guide to SQL Server NOT NULL Constraint By Examples
April 11, 2020 - The SQL Server NOT NULL constraints simply specify that a column must not assume the NULL. The following example creates a table with NOT NULL constraints for the columns: first_name, last_name, and email: CREATE SCHEMA hr; GO CREATE TABLE hr.persons( person_id INT IDENTITY PRIMARY KEY, first_name ...
Quora
quora.com › How-do-you-apply-a-non-null-constraint-in-SQL
How to apply a non-null constraint in SQL - Quora
Answer (1 of 4): “Enforcement” of constraints is done automatically by the database engine itself, so “you” - the database engine user - don’t need to actively do anything to cause constraints to be “applied”, other than make sure your code respects the constraints.
Microsoft Learn
learn.microsoft.com › en-us › answers › questions › 2238850 › adding-conditional-not-null-constraint-to-table
Adding Conditional Not Null Constraint to Table - Microsoft Q&A
March 25, 2025 - ALTER TABLE [dbo].[Test] WITH CHECK ADD CONSTRAINT [CN_Test_Flag] CHECK ( (Flag = 0 AND Column2 IS NOT NULL AND Column2 <> '' AND Column3 IS NOT NULL AND Column3 <> '') OR (Flag = 1 AND Column2 IS NULL AND Column3 IS NULL) ) GO ... If the answer is helpful, please click "Accept Answer" and upvote it. ... Not sure what you mean.
SQLZealots
sqlzealots.com › 2021 › 05 › 29 › not-null-constraint-in-sql-server
NOT NULL Constraint in SQL Server – SQLZealots
May 29, 2021 - NOT NULL constraints are important constraints in SQL Server to ensure the column defined on never accepts NULL values. By default, column accepts NULL value in SQL Server. If we need to ensure the column should not accept NULL values, then ...
Database Guide
database.guide › understanding-the-not-null-constraint-in-sql
Understanding the NOT NULL Constraint in SQL
This is called a NOT NULL constraint. The NOT NULL constraint is used to ensure that a column cannot have a NULL value. When a column is defined as NOT NULL, it becomes mandatory to insert a value in that column for every row in the table.