Why INSERT matters in SQL - Challenge Your Understanding

Challenge - 5 Problems

❓ query_result

intermediate

What is the result of this INSERT followed by SELECT?

Consider a table students with columns id (integer) and name (text). Initially, the table is empty.

What will be the output of the following SQL commands?

INSERT INTO students (id, name) VALUES (1, 'Alice');
SELECT * FROM students;

SQL

INSERT INTO students (id, name) VALUES (1, 'Alice');
SELECT * FROM students;

A 1 | Alice

B Empty result set

C Syntax error

D NULL | NULL

💡 Hint

Think about what happens when you insert a row and then select all rows.

After inserting one row with id=1 and name='Alice', selecting all rows returns that row.

🧠 Conceptual

intermediate

Why is INSERT important in databases?

Which of the following best explains why the INSERT statement is important in databases?

A It deletes data from the database to free space.

B It changes the structure of the database tables.

C It adds new data to the database, allowing storage of information.

D It retrieves data from the database for viewing.

💡 Hint

Think about what INSERT does compared to DELETE or SELECT.

INSERT adds new rows (records) to tables, which is essential for storing new information.

📝 Syntax

advanced

Which INSERT statement is syntactically correct?

Given a table products with columns product_id (integer) and product_name (text), which of the following INSERT statements is correct?

A INSERT INTO products (product_id, product_name) VALUE (101, 'Pen');

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

C INSERT products (product_id, product_name) VALUES (101, 'Pen');

D INSERT INTO products (product_id product_name) VALUES (101, 'Pen');

💡 Hint

Check the syntax for the INSERT INTO statement carefully.

Option B uses correct syntax: INSERT INTO table VALUES (...);. Option B misses INTO. Option B misses comma between columns. Option B uses VALUE instead of VALUES.

❓ optimization

advanced

Which INSERT method is more efficient for adding many rows?

You need to add 1000 new rows to a table orders. Which method is generally more efficient?

A Using SELECT without INSERT.

B 1000 separate INSERT statements, one per row.

C Using DELETE then INSERT for each row.

D One INSERT statement with 1000 rows listed in VALUES clause.

💡 Hint

Think about how many times the database has to process commands.

One INSERT with many rows reduces overhead and is faster than many single-row INSERTs.

🔧 Debug

expert

What error does this INSERT cause?

Given a table employees with columns id (integer, primary key) and name (text), what error will this query cause?

INSERT INTO employees (id, name) VALUES (1, 'John');
INSERT INTO employees (id, name) VALUES (1, 'Jane');

A Primary key violation error

B Syntax error

C No error, both rows inserted

D Foreign key violation error

💡 Hint

Think about what happens if you insert two rows with the same primary key.

The primary key must be unique. Inserting two rows with the same id causes a primary key violation.