How to Set a Column Value to Null in SQL?

In this article, we will look into how you can set the column value to Null in SQL.

Firstly, let’s create a table using CREATE TABLE command:

-- create a table
CREATE TABLE students (Sr_No integer,Name varchar(20), Gender varchar(2));
-- insert some values
INSERT INTO students VALUES (1, 'Nikita', 'F');
INSERT INTO students VALUES (2, 'Akshit', 'M');
INSERT INTO students VALUES (3, 'Ritesh', 'F');
INSERT INTO students VALUES (4, 'Himani', 'F');
-- fetch some values
SELECT * FROM students ;

The table would look like this:

To UPDATE Column value, use the below command:

 UPDATE TABLE [TABLE_NAME]

To set column value to NULL use syntax:

 update [TABLE_NAME] set [COLUMN_NAME] = NULL where [CRITERIA] 

Example: For the above table

update students set Gender = NULL where Gender='F';
SELECT * FROM students ;

Output:

Column value can also be set to NULL without specifying the ‘where’ condition.

Example:

update students set Gender = NULL;
SELECT * FROM students ;

Output:

If you have set a constraint that a particular column value can not be NULL, and later try to set it as NULL, then it will generate an error.

Example:

-- create a table
CREATE TABLE students (Sr_No integer,Name varchar(20), Gender varchar(2) NOT NULL);
-- insert some values
INSERT INTO students VALUES (1, 'Nikita', 'F');
INSERT INTO students VALUES (2, 'Akshit', 'M');
INSERT INTO students VALUES (3, 'Ritesh', 'F');
INSERT INTO students VALUES (4, 'Himani', 'F');
-- fetch some values
SELECT * FROM students ;

Output:

ERROR: Gender may not be NULL.

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