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PostgreSQL INSERT, UPDATE, and DELETE Commands

Introduction
Inserting and updating NULLs
8. IS NULL in DELETE
Conditions in UPDATE and DELETE
Updating the list of columns in one query
Using values from another column
Return rows in INSERT, UPDATE, DELETE
Summary

Instruction

Great! You know how to use IS NULL in an UPDATE statement. Now it's time to get familiar with IS NULL in another statement: DELETE. The command below explains why it is sometimes worth using IS NULL with DELETE:

DELETE FROM student
WHERE last_name IS NULL;

This command removes all students without a last name from the database. A last name is a very important way to identify a student, and a record without it is not useful. Here, we use IS NULL to check if the last_name column has a NULL in it. The query leaves only student records with existing last names in the database.

Exercise

A group of students weren't scored on an oral exam, so the exam was canceled. The results from this exam have to be removed. Write a query to remove these records.