Common INSERT errors and fixes in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a new row into the users table with a name and age.

SQL

INSERT INTO users (name, age) VALUES ([1], 30);

Drag options to blanks, or click blank then click option'

A'Alice'

BAlice

C"Alice"

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around text values.

Using double quotes instead of single quotes for text.

The value for a text column must be enclosed in single quotes in SQL.

2fill in blank

medium

Complete the code to insert a row with all columns in the products table.

SQL

INSERT INTO products VALUES ([1], 'Laptop', 999.99);

Drag options to blanks, or click blank then click option'

A'1'

B1

Cid

DNULL

Attempts:

3 left

💡 Hint

Common Mistakes

Putting numeric values inside quotes.

Not matching the number of values to the number of columns.

When inserting values without specifying columns, you must provide values in the correct order and types. Numeric values like IDs should not be quoted.

3fill in blank

hard

Fix the error in the INSERT statement by completing the missing keyword.

SQL

INSERT [1] users (name, age) VALUES ('Bob', 25);

Drag options to blanks, or click blank then click option'

ATO

BIN

CINTO

DON

Attempts:

3 left

💡 Hint

Common Mistakes

Using TO or IN instead of INTO.

Omitting the keyword after INSERT.

The correct syntax for inserting data requires the keyword INTO after INSERT.

4fill in blank

hard

Fill both blanks to insert a row with only the name column specified.

SQL

INSERT INTO users ([1]) VALUES ([2]);

Drag options to blanks, or click blank then click option'

Aname

B'Charlie'

Cage

D30

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching columns and values.

Forgetting quotes around text values.

When inserting only one column, specify its name and provide a matching value in quotes if it is text.

5fill in blank

hard

Fill all three blanks to insert a new product with id, name, and price.

SQL

INSERT INTO products ([1], [2], [3]) VALUES (101, 'Tablet', 299.99);

Drag options to blanks, or click blank then click option'

Aid

Bname

Cprice

Dquantity

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong column names that don't match the table.

Mismatching the order of columns and values.

Specify the correct column names matching the values you want to insert.

Practice

1. What is a common cause of an INSERT statement failing in SQL?

easy

A. Adding extra spaces between keywords

B. Using SELECT instead of INSERT

C. Missing a value for a column that does not allow NULLs

D. Writing the table name in lowercase

Solution

1. Step 1: Understand column constraints

   Columns that do not allow NULL values must have a value provided during insert.

2. Step 2: Identify missing values impact

   If a required column is missing a value, the insert will fail with an error.

3. Final Answer:

   Missing a value for a column that does not allow NULLs -> Option C

4. Quick Check:

   Required columns need values [OK]

Hint: Always provide values for NOT NULL columns [OK]

Common Mistakes:

• Ignoring NOT NULL constraints
• Assuming case sensitivity causes errors
• Confusing SELECT with INSERT

2. Which of the following INSERT statements is syntactically correct for a table users(id, name)?

easy

A. INSERT INTO users VALUES (1, 'Alice');

B. INSERT users INTO VALUES (1, 'Alice');

C. INSERT INTO users (1, 'Alice');

D. INSERT INTO users VALUES 1, 'Alice';

Solution

1. Step 1: Review correct INSERT syntax

   The correct syntax is: INSERT INTO table_name VALUES (value1, value2, ...);

2. Step 2: Check each option

   INSERT INTO users VALUES (1, 'Alice'); matches the correct syntax exactly; others have misplaced keywords or missing parentheses.

3. Final Answer:

   INSERT INTO users VALUES (1, 'Alice'); -> Option A

4. Quick Check:

   INSERT INTO table VALUES (...) [OK]

Hint: Remember: INSERT INTO table VALUES (values) [OK]

Common Mistakes:

• Misplacing keywords order
• Omitting parentheses around values
• Using wrong keyword sequence

3. Given the table products(id INT PRIMARY KEY, name VARCHAR(20)), what happens when you run:
INSERT INTO products VALUES (1, 'Pen');
INSERT INTO products VALUES (1, 'Pencil');

medium

A. Syntax error on second insert

B. Both rows are inserted successfully

C. Second insert overwrites the first row

D. Second insert fails due to duplicate primary key

Solution

1. Step 1: Understand primary key constraint

   Primary keys must be unique; duplicate values cause insert failure.

2. Step 2: Analyze the inserts

   The first insert adds id=1. The second tries to add id=1 again, causing a duplicate key error.

3. Final Answer:

   Second insert fails due to duplicate primary key -> Option D

4. Quick Check:

   Primary key duplicates cause insert errors [OK]

Hint: Primary keys must be unique; duplicates fail [OK]

Common Mistakes:

• Assuming duplicates overwrite existing rows
• Ignoring primary key uniqueness
• Expecting syntax error instead of constraint error

4. You run this query:
INSERT INTO employees (id, name, age) VALUES (5, 'John');
What is the error and how to fix it?

medium

A. Syntax error: missing value for age; add the missing value

B. No error; query runs fine

C. Wrong table name; change employees to employee

D. Age column must be removed from column list

Solution

1. Step 1: Check column-value count

   Columns listed are 3, but only 2 values provided; this causes an error.

2. Step 2: Fix by adding missing value

   Provide a value for age or remove it from the column list to match values count.

3. Final Answer:

   Syntax error: missing value for age; add the missing value -> Option A

4. Quick Check:

   Columns and values count must match [OK]

Hint: Match columns count with values count [OK]

Common Mistakes:

• Providing fewer values than columns
• Assuming missing values default automatically
• Ignoring syntax errors from mismatch

5. You want to insert multiple rows into orders(order_id INT PRIMARY KEY, product VARCHAR(50), quantity INT). Which statement correctly inserts two rows without errors?

hard

A. INSERT INTO orders VALUES (101, 'Book', 3); INSERT INTO orders VALUES (101, 'Pen', 5);

B. INSERT INTO orders VALUES (101, 'Book', 3), (102, 'Pen', 5);

C. INSERT INTO orders (order_id, product) VALUES (101, 'Book'), (102, 'Pen');

D. INSERT INTO orders VALUES (101, 'Book', 'three'), (102, 'Pen', 5);

Solution

1. Step 1: Check multiple row insert syntax

   INSERT INTO orders VALUES (101, 'Book', 3), (102, 'Pen', 5); uses correct syntax to insert multiple rows in one statement.

2. Step 2: Validate data types and uniqueness

   INSERT INTO orders VALUES (101, 'Book', 3), (102, 'Pen', 5); provides unique order_id and correct data types; others have duplicates, missing columns, or wrong types.

3. Final Answer:

   INSERT INTO orders VALUES (101, 'Book', 3), (102, 'Pen', 5); -> Option B

4. Quick Check:

   Multiple rows insert with unique keys and correct types [OK]

Hint: Use comma-separated rows with matching columns [OK]

Common Mistakes:

• Duplicate primary keys in multiple inserts
• Missing required columns in multi-row insert
• Wrong data types causing errors