How to express not equal to null in sql

The expression that is not equal to NULL in SQL is: IS NOT NULL. This operator checks whether an expression is not equal to NULL and returns a Boolean value: TRUE if the expression is not equal to NULL; otherwise, FALSE.

The representation of not equal to NULL in SQL

In SQL, not equal to NULL can be represented by the following operators :

IS NOT NULL

Detailed description:

• IS NOT NULL Operation operator is used to check whether an expression is not equal to NULL.
• It returns a Boolean value: TRUE if the expression is not equal to NULL; otherwise, FALSE.
• This operator can be applied to any expression that can return a NULL value, such as a column, function, or subquery.

Example:

SELECT * FROM table_name WHERE column_name IS NOT NULL;

This query will return all the column_name columns in the table_name table that are not equal to NULL OK.

Note:

• IS NOT NULL is different from NOT NULL. NOT NULL is a constraint used to force a column not to store NULL values ​​when the table is created, while IS NOT NULL is an operator used to check whether an expression is not equal to NULL.
• The IS NOT NULL operator also returns NULL if the expression itself is NULL.

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