LearnViz CompSci
Home / Learn / Databases / INSERT, UPDATE, DELETE

Beginner Topic 11 of 51 Databases

INSERT, UPDATE, DELETE

Statements that modify stored rows.

How it works

INSERT adds new rows, UPDATE changes values in existing rows matching a WHERE condition and DELETE removes rows. Together with SELECT they make up CRUD operations. Statements can affect many rows at once, can be wrapped in transactions to be committed or rolled back, and fire constraints and triggers. Many databases support upserts, such as INSERT ON CONFLICT, and RETURNING clauses to read modified rows.

Step-by-step walkthrough

  1. INSERT creates a new row with values.
  2. UPDATE changes columns of rows matching WHERE.
  3. DELETE removes rows matching WHERE.
  4. Forgetting WHERE affects every row.
  5. Wrap risky changes in a transaction so they can be rolled back.

Where it is used

Recording orders, updating stock levels, correcting data, removing expired sessions and loading bulk data use these statements. Batching inserts is much faster than many single-row statements.

Common pitfall

Forgetting the WHERE clause on UPDATE or DELETE changes every row, a famous disaster; run a SELECT with the same condition first and use transactions. Deleting parents violates foreign keys. Large updates lock rows and generate big logs, so process in batches. Soft deletes with a flag preserve history but complicate queries.

Where it fits in the course

INSERT, UPDATE, DELETE is topic 11 of 51 in Databases, rated Beginner. It follows ORDER BY and LIMIT. The next topic is Aggregate Functions.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Databases quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is INSERT, UPDATE, DELETE?
Statements that modify stored rows. It belongs to Databases and is a beginner-level topic.
Where do people use INSERT, UPDATE, DELETE?
Recording orders, updating stock levels, correcting data, removing expired sessions and loading bulk data use these statements.
What is the most common mistake with INSERT, UPDATE, DELETE?
Forgetting the WHERE clause on UPDATE or DELETE changes every row, a famous disaster; run a SELECT with the same condition first and use transactions.
What should I learn before this topic?
Start with ORDER BY and LIMIT, the topic just before it in Databases.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Databases quiz.
Is INSERT, UPDATE, DELETE hard to learn?
It is a Beginner topic, so it works as an entry point. If the terms are new, read the explanation twice and try the visualizer before the quiz.
How long does it take to learn INSERT, UPDATE, DELETE?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to INSERT, UPDATE, DELETE?
ORDER BY and LIMIT, Aggregate Functions, WHERE and Filtering are closely connected. The full list is in the related topics section of this page.
What should I study after INSERT, UPDATE, DELETE?
Continue with Aggregate Functions, the next topic in Databases.

Related topics