Bird
Raised Fist0
SQLquery~5 mins

UPDATE with WHERE condition in SQL

Choose your learning style10 modes available
LearnWhyDeepVisualTryChallengeProjectRecallTime
Introduction

We use UPDATE with WHERE to change specific data in a table, not everything. It helps us fix or change only the rows we want.

You want to fix a wrong phone number for one customer in your contacts list.
You need to change the status of orders that are shipped to 'delivered'.
You want to update the price of a specific product in your store.
You need to mark certain employees as inactive based on their ID.
You want to correct the address of a single user without affecting others.
Syntax
SQL
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

The WHERE clause limits which rows get updated.

Without WHERE, all rows in the table will be updated!

Examples
Updates salary only for the employee with ID 101.
SQL
UPDATE employees
SET salary = 5000
WHERE employee_id = 101;
Increases price by 10% for all products in the 'Books' category.
SQL
UPDATE products
SET price = price * 1.1
WHERE category = 'Books';
Marks orders before 2024 as delivered.
SQL
UPDATE orders
SET status = 'delivered'
WHERE order_date < '2024-01-01';
Sample Program

This example creates a users table, adds three users, then updates Bob's email using WHERE to target only his row.

SQL
CREATE TABLE users (
  id INT PRIMARY KEY,
  name VARCHAR(50),
  email VARCHAR(50)
);

INSERT INTO users (id, name, email) VALUES
(1, 'Alice', 'alice@example.com'),
(2, 'Bob', 'bob@example.com'),
(3, 'Charlie', 'charlie@example.com');

UPDATE users
SET email = 'bob.new@example.com'
WHERE id = 2;

SELECT * FROM users ORDER BY id;
OutputSuccess
Important Notes

Always double-check your WHERE condition to avoid unwanted updates.

You can update multiple columns by separating them with commas.

Use ORDER BY in SELECT to see results in a clear order after update.

Summary

UPDATE with WHERE changes only the rows you want.

Without WHERE, all rows get updated--be careful!

You can update one or many columns at once.

Practice

(1/5)
1.

What does the WHERE clause do in an UPDATE statement?

easy
A. It adds new rows to the table.
B. It changes the table structure.
C. It limits which rows get updated.
D. It deletes rows from the table.

Solution

  1. Step 1: Understand the purpose of UPDATE

    The UPDATE statement changes data in existing rows of a table.

  2. Step 2: Role of WHERE clause in UPDATE

    The WHERE clause specifies which rows should be changed, so only those rows are updated.

  3. Final Answer:

    It limits which rows get updated. -> Option C

  4. Quick Check:

    WHERE clause = row filter [OK]
Hint: WHERE filters rows to update only those needed [OK]
Common Mistakes:
  • Thinking WHERE adds or deletes rows
  • Believing UPDATE changes table structure
  • Ignoring WHERE updates all rows
2.

Which of the following is the correct syntax to update the salary to 5000 for employees with id 3?

UPDATE employees SET salary = 5000 WHERE id = 3;
easy
A. UPDATE employees SET salary 5000 WHERE id = 3;
B. UPDATE employees salary = 5000 WHERE id = 3;
C. UPDATE employees SET salary = 5000 id = 3;
D. UPDATE employees SET salary = 5000 WHERE id = 3;

Solution

  1. Step 1: Check UPDATE syntax

    The correct syntax requires SET before column assignment and WHERE for condition.

  2. Step 2: Validate each option

    UPDATE employees SET salary = 5000 WHERE id = 3; uses SET and WHERE correctly; others miss SET or WHERE or have wrong syntax.

  3. Final Answer:

    UPDATE employees SET salary = 5000 WHERE id = 3; -> Option D

  4. Quick Check:

    SET + WHERE = correct UPDATE syntax [OK]
Hint: Always use SET before column assignments in UPDATE [OK]
Common Mistakes:
  • Omitting SET keyword
  • Forgetting WHERE clause
  • Missing equal sign (=) in assignment
3.

Given the table products:

id | name    | price
---+---------+-------
1  | Pen     | 10
2  | Pencil  | 5
3  | Eraser  | 3

What will be the result of this query?

UPDATE products SET price = price + 2 WHERE price < 10;
medium
A. All products will have their price increased by 2.
B. Only products with price less than 10 will have their price increased by 2.
C. No products will be updated because price is not changed.
D. Syntax error due to missing WHERE clause.

Solution

  1. Step 1: Identify rows matching WHERE condition

    Prices less than 10 are 5 and 3 (Pencil and Eraser).

  2. Step 2: Apply UPDATE only to matching rows

    Only Pencil and Eraser prices increase by 2, Pen remains 10.

  3. Final Answer:

    Only products with price less than 10 will have their price increased by 2. -> Option B

  4. Quick Check:

    WHERE filters rows updated [OK]
Hint: WHERE limits which rows get updated, others stay same [OK]
Common Mistakes:
  • Assuming all rows update without WHERE
  • Thinking price must be reset, not incremented
  • Confusing syntax error with correct query
4.

Find the error in this query:

UPDATE employees SET salary = 6000 WHERE;
medium
A. Missing condition after WHERE clause.
B. Missing SET keyword.
C. Incorrect table name.
D. No error, query is correct.

Solution

  1. Step 1: Analyze the WHERE clause

    The WHERE clause is incomplete; it must have a condition after it.

  2. Step 2: Check other parts of query

    SET keyword and table name are correct; only WHERE is incomplete.

  3. Final Answer:

    Missing condition after WHERE clause. -> Option A

  4. Quick Check:

    WHERE needs a condition [OK]
Hint: WHERE must always have a condition after it [OK]
Common Mistakes:
  • Leaving WHERE empty
  • Confusing missing SET with WHERE error
  • Assuming query runs without WHERE condition
5.

You have a table students with columns id, name, and grade. You want to increase the grade by 5 for all students who scored less than 50, but not exceed 50 after update. Which query correctly does this?

hard
A. UPDATE students SET grade = CASE WHEN grade + 5 > 50 THEN 50 ELSE grade + 5 END WHERE grade < 50;
B. UPDATE students SET grade = grade + 5 WHERE grade < 50 AND grade + 5 <= 50;
C. UPDATE students SET grade = grade + 5 WHERE grade < 50;
D. UPDATE students SET grade = 50 WHERE grade < 50;

Solution

  1. Step 1: Understand the requirement

    Increase grade by 5 only for grades less than 50, but cap max grade at 50.

  2. Step 2: Analyze each option

    UPDATE students SET grade = 50 WHERE grade < 50; sets all below 50 to 50 directly, no increase by 5. UPDATE students SET grade = grade + 5 WHERE grade < 50 AND grade + 5 <= 50; increases by 5 only if result ≤ 50, skipping some rows. UPDATE students SET grade = grade + 5 WHERE grade < 50; increases by 5 without capping at 50. UPDATE students SET grade = CASE WHEN grade + 5 > 50 THEN 50 ELSE grade + 5 END WHERE grade < 50; uses CASE to increase by 5 but caps at 50 correctly.

  3. Final Answer:

    UPDATE students SET grade = CASE WHEN grade + 5 > 50 THEN 50 ELSE grade + 5 END WHERE grade < 50; -> Option A

  4. Quick Check:

    Use CASE to cap values in UPDATE [OK]
Hint: Use CASE in UPDATE to handle conditional value changes [OK]
Common Mistakes:
  • Not capping grade at 50
  • Updating all rows without WHERE
  • Skipping rows that would exceed 50
Recommended

Ready to prove it?

Pass the test and this pattern moves unknown strong while earning +1 Grip toward your certificate.

10 questions~5 mineasy hard