INSERT INTO single row in MySQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the result of this INSERT statement?

Given the table employees with columns id (int), name (varchar), and age (int), what will be the result after running this query?

INSERT INTO employees (id, name, age) VALUES (1, 'Alice', 30);

Assume the table was empty before.

MySQL

INSERT INTO employees (id, name, age) VALUES (1, 'Alice', 30);

A One new row is added with id=1, name='Alice', age=30

B No rows are added because the table is empty

C An error occurs because the id column is missing

D Two rows are added with the same data

💡 Hint

Think about what INSERT INTO does when the table is empty.

The INSERT INTO statement adds exactly one row with the specified values into the table. Since the table was empty, now it has one row with the given data.

📝 Syntax

intermediate

Which INSERT statement is syntactically correct?

Choose the correct INSERT statement to add a single row into the products table with columns product_id, product_name, and price.

A INSERT INTO products (product_id, product_name, price) VALUES 101, 'Pen', 1.5;

B INSERT products INTO VALUES (101, 'Pen', 1.5);

C INSERT INTO products VALUES (101, 'Pen', 1.5);

D INSERT INTO products (product_id, product_name, price) VALUE (101, 'Pen', 1.5);

💡 Hint

Remember the correct order of keywords in an INSERT statement.

Option C uses the correct syntax: INSERT INTO table VALUES (...). Option C has wrong keyword order. Option C misses parentheses around VALUES. Option C uses VALUE instead of VALUES, which is invalid in MySQL.

❓ optimization

advanced

Which INSERT statement is more efficient for inserting a single row?

You want to insert a single row into the orders table with columns order_id, customer, and amount. Which option is more efficient and why?

A INSERT INTO orders SET order_id=5001, customer='John Doe', amount=250;

B INSERT INTO orders VALUES (5001, 'John Doe', 250);

C INSERT INTO orders (order_id, customer) VALUES (5001, 'John Doe');

D INSERT INTO orders (order_id, customer, amount) VALUES (5001, 'John Doe', 250);

💡 Hint

Consider clarity and explicitness in specifying columns.

Option D explicitly lists columns and values, which is clearer and safer if table structure changes. Option D relies on column order, which can cause errors. Option D uses SET syntax which is valid but less common and may be less optimized. Option D misses the amount column, causing an error if it is NOT NULL.

🔧 Debug

advanced

Why does this INSERT statement fail?

Given the table students with columns id (int, primary key), name (varchar), and age (int NOT NULL), why does this query fail?

INSERT INTO students (id, name) VALUES (10, 'Emma');

MySQL

INSERT INTO students (id, name) VALUES (10, 'Emma');

A Because the table students does not exist

B Because the age column is NOT NULL and no value was provided

C Because the name column cannot be inserted without age

D Because the id column is missing in the VALUES clause

💡 Hint

Check the NOT NULL constraints on columns.

The age column is NOT NULL, so it requires a value on insert. Omitting it causes an error.

🧠 Conceptual

expert

What happens if you insert a row with a duplicate primary key?

Consider a table inventory with item_id as the primary key. What happens if you run this query twice?

INSERT INTO inventory (item_id, item_name) VALUES (100, 'Notebook');

MySQL

INSERT INTO inventory (item_id, item_name) VALUES (100, 'Notebook');

A The first insert succeeds; the second insert fails with a duplicate key error

B Both inserts succeed and create two identical rows

C The second insert updates the existing row with new data

D Both inserts fail because primary keys cannot be inserted

💡 Hint

Think about primary key uniqueness constraints.

Primary keys must be unique. The first insert adds the row. The second insert tries to add a duplicate key and fails with an error.