PostgreSQL IS NULL condition

Preamble

PostgreSQL IS NULL condition is used to check the value of NULL in SELECT, INSERT, UPDATE or DELETE operators.

PostgreSQL IS NULL condition

IS expression NULL

Parameters and arguments

• expression – A value to check if it is a NULL value.

Note:

• If the expression is NULL, the condition is evaluated as TRUE.
• If the expression is not a value of NULL, the condition is evaluated as FALSE.

Example of an IS NULL condition with the SELECT operator

Let’s consider an example of using PostgreSQL IS NULL in the SELECT operator:

SELECT *
FROM empls
WHERE first_number IS NULL;

This example of PostgreSQL IS NULL will return all records from the employee table where first_name contains the value NULL.

Example of a condition with the INSERT operator

Then let’s consider an example of using PostgreSQL IS NULL in the INSERT operator:

INSERT INTO contacts
(first_name, last_name)
SELECT first_name, last_name
FROM empls
WHERE empl_number IS NULL;

This example of PostgreSQL IS NULL will insert records into the contacts table where employee_number contains the value NULL.

Example of a condition with UPDATE operator

Next Let’s consider an example of using PostgreSQL IS NULL in UPDATE operator:

UPDATE empls
SET status = 'Not Active'
WHERE last_name IS NULL;

This example of PostgreSQL IS NULL will update records in the employee table where last_name contains the value NULL.

Example of a condition with the DELETE operator

Next Let’s consider an example of using PostgreSQL IS NULL in DELETE operator:

DELETE FROM empls
WHERE empl_number IS NULL;

This example of PostgreSQL IS NULL will remove all records from the contacts table where employee_number contains the value NULL.

PostgreSQL: Coalesce | Course

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