SQL INSERT, UPDATE and DELETE Practice

Practise changing data safely with INSERT, UPDATE and DELETE, and changing tables with CREATE TABLE and ALTER TABLE.

Beginner7 problemsUpdated October 23, 2026

Review first: INSERT, UPDATE, DELETE, CREATE TABLE, ALTER TABLE, Constraints

Each problem starts from this tasks table, so changes made in one problem do not carry over to the next:

task_id	title	status	priority	assignee
1	Write report	open	2	Asha
2	Fix login bug	in_progress	1	Ravi
3	Update docs	open	3	NULL
4	Plan sprint	done	2	Meera
5	Review PR	open	1	Ravi

Each solution ends with a SELECT so you can see the effect of the change.

Try your answers on these tables in the SQL Playground

1.Add a task
Beginner
Add a task with id 6, title Prepare demo, status open, priority 2, assigned to Meera. Then show the new row.
Show hint
List the columns after the table name, then the values in the same order.
Show solution
SQLRun
INSERT INTO tasks (task_id, title, status, priority, assignee) VALUES (6, 'Prepare demo', 'open', 2, 'Meera'); SELECT * FROM tasks WHERE task_id = 6;
Output
task_id | title | status | priority | assignee --------+--------------+--------+----------+--------- 6 | Prepare demo | open | 2 | Meera
Naming the columns is optional when you supply a value for every column, but it is safer. The statement keeps working if someone later adds or reorders columns.
2.Add several tasks at once
Beginner
In one INSERT statement, add these two tasks, then return the total number of tasks as total_tasks:
- id 6, Book venue, open, priority 3, no assignee yet
- id 7, Send invites, open, priority 2, assigned to Asha
Show hint
Separate each row's values with a comma after VALUES. Use NULL for the missing assignee.
Show solution
SQLRun
INSERT INTO tasks (task_id, title, status, priority, assignee) VALUES (6, 'Book venue', 'open', 3, NULL), (7, 'Send invites', 'open', 2, 'Asha'); SELECT COUNT(*) AS total_tasks FROM tasks;
Output
total_tasks ----------- 7

3.Close a task

Beginner

Task 2 is finished. Set its status to done, then list the task_id, title and status of every done task.

Show hint

UPDATE ... SET ... WHERE. Without the WHERE, every task would change.

Show solution

SQLRun

UPDATE tasks
SET status = 'done'
WHERE task_id = 2;

SELECT task_id, title, status
FROM tasks
WHERE status = 'done'
ORDER BY task_id;

Output

task_id | title         | status
--------+---------------+-------
2       | Fix login bug | done
4       | Plan sprint   | done

4.Assign the unassigned

Beginner

Give every task that has no assignee to Kiran and set its priority to 1. Then show all tasks with their assignee and priority.

Show hint

You can set several columns in one UPDATE, separated by commas. Find the rows with IS NULL.

Show solution

SQLRun

UPDATE tasks
SET assignee = 'Kiran', priority = 1
WHERE assignee IS NULL;

SELECT task_id, title, assignee, priority
FROM tasks
ORDER BY task_id;

Output

task_id | title         | assignee | priority
--------+---------------+----------+---------
1       | Write report  | Asha     | 2
2       | Fix login bug | Ravi     | 1
3       | Update docs   | Kiran    | 1
4       | Plan sprint   | Meera    | 2
5       | Review PR     | Ravi     | 1

5.Remove finished tasks
Beginner
Delete every task whose status is done, then list the remaining tasks' task_id, title and status.
Show hint
DELETE FROM with a WHERE clause. Run the same WHERE in a SELECT first to check which rows it matches.
Show solution
SQLRun
DELETE FROM tasks WHERE status = 'done'; SELECT task_id, title, status FROM tasks ORDER BY task_id;
Output
task_id | title | status --------+---------------+------------ 1 | Write report | open 2 | Fix login bug | in_progress 3 | Update docs | open 5 | Review PR | open
A good habit before any DELETE is to run SELECT * FROM tasks WHERE status = 'done' first. If it returns exactly the rows you expect, change SELECT * to DELETE.
6.Create a table with constraints
Beginner
Create a projects table with:
- project_id: an integer primary key
- name: text up to 100 characters, required and unique
- budget: a whole number that cannot be negative
- start_date: a date
Insert the project 1, 'Website Redesign', 250000, '2026-11-01', then select the project_id and name of all projects.
Show hint
Use PRIMARY KEY, NOT NULL, UNIQUE and a CHECK (budget >= 0) constraint.
Show solution
SQLRun
CREATE TABLE projects ( project_id INTEGER PRIMARY KEY, name VARCHAR(100) NOT NULL UNIQUE, budget INTEGER CHECK (budget >= 0), start_date DATE ); INSERT INTO projects (project_id, name, budget, start_date) VALUES (1, 'Website Redesign', 250000, '2026-11-01'); SELECT project_id, name FROM projects;
Output
project_id | name -----------+----------------- 1 | Website Redesign
With these constraints, the database itself rejects bad data. Inserting a second project called Website Redesign, a project with no name, or a negative budget fails with an error instead of storing a wrong row.

7.Add a column

Beginner

Add a due_date column (type DATE) to tasks. Set it to 2026-11-15 for the priority-1 tasks, then show every task's task_id, title and due_date.

Show hint

ALTER TABLE ... ADD COLUMN, then an UPDATE. Existing rows get NULL in the new column.

Show solution

SQLRun

ALTER TABLE tasks ADD COLUMN due_date DATE;

UPDATE tasks
SET due_date = '2026-11-15'
WHERE priority = 1;

SELECT task_id, title, due_date
FROM tasks
ORDER BY task_id;

Output

task_id | title         | due_date
--------+---------------+-----------
1       | Write report  | NULL
2       | Fix login bug | 2026-11-15
3       | Update docs   | NULL
4       | Plan sprint   | NULL
5       | Review PR     | 2026-11-15

SQL Server and Oracle write ADD without the word COLUMN (Oracle also wraps the definition in brackets). PostgreSQL, MySQL and SQLite accept ADD COLUMN.

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