REPLACE function in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to replace all occurrences of 'cat' with 'dog' in the column animal_name.

SQL

SELECT REPLACE(animal_name, 'cat', [1]) AS new_name FROM animals;

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

A'dog'

B'bird'

C'fish'

D'lion'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong replacement string.

Forgetting to put quotes around the replacement string.

The REPLACE function replaces all occurrences of the second argument with the third argument. Here, 'cat' is replaced with 'dog'.

2fill in blank

medium

Complete the code to replace all spaces with underscores in the column product_name.

SQL

SELECT REPLACE(product_name, [1], '_') AS new_product FROM products;

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

A'-'

B'_'

C' '

D','

Attempts:

3 left

💡 Hint

Common Mistakes

Using underscore '_' as the string to replace instead of space.

Forgetting to use quotes around the space character.

To replace spaces, the second argument must be a space character ' '.

3fill in blank

hard

Fix the error in the code to replace 'old' with 'new' in the description column.

SQL

SELECT REPLACE(description, 'old', [1]) FROM items;

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

Anew

Bnew'

C"new"

D'new'

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the replacement string.

Using double quotes which may not be valid in all SQL dialects.

String literals in SQL must be enclosed in single quotes. So 'new' is correct.

4fill in blank

hard

Fill both blanks to replace all occurrences of 'blue' with 'red' in the color column and rename the output as new_color.

SQL

SELECT REPLACE([1], [2], 'red') AS new_color FROM colors;

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

Acolor

B'blue'

C'red'

Dshade

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the column name and string to replace.

Forgetting quotes around the string 'blue'.

The first blank is the column name 'color'. The second blank is the string to replace, which is 'blue'.

5fill in blank

hard

Fill all three blanks to replace '2023' with '2024' in the event_year column, rename the output as updated_year, and select from the events table.

SQL

SELECT REPLACE([1], [2], [3]) AS updated_year FROM events;

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

Aevent_year

B'2023'

C'2024'

D'2025'

Attempts:

3 left

💡 Hint

Common Mistakes

Using numbers without quotes.

Mixing up the strings to replace and replacement.

The first blank is the column name 'event_year'. The second blank is the string to replace '2023'. The third blank is the replacement string '2024'.

Practice

1. What does the SQL REPLACE function do?

easy

A. It converts all characters in a string to uppercase.

B. It deletes a substring from a string without replacement.

C. It extracts a substring from a string based on position.

D. It replaces all occurrences of a specified substring within a string with another substring.

Solution

1. Step 1: Understand the purpose of REPLACE

   The REPLACE function is designed to find all instances of a substring in a string and swap them with another substring.

2. Step 2: Compare with other string functions

   Unlike deleting or extracting substrings, REPLACE changes the content by substitution.

3. Final Answer:

   It replaces all occurrences of a specified substring within a string with another substring. -> Option D

4. Quick Check:

   REPLACE swaps substrings = A [OK]

Hint: REPLACE swaps all target text with new text [OK]

Common Mistakes:

• Thinking REPLACE deletes text without substitution
• Confusing REPLACE with substring extraction
• Assuming REPLACE changes case of text

2. Which of the following is the correct syntax for the SQL REPLACE function?

easy

A. REPLACE(string, old_substring, new_substring)

B. REPLACE(old_substring, new_substring, string)

C. REPLACE(string, new_substring, old_substring)

D. REPLACE(new_substring, string, old_substring)

Solution

1. Step 1: Recall REPLACE function parameter order

   The correct order is the original string first, then the substring to replace, then the new substring.

2. Step 2: Verify each option

   Only REPLACE(string, old_substring, new_substring) follows the correct order: REPLACE(string, old_substring, new_substring).

3. Final Answer:

   REPLACE(string, old_substring, new_substring) -> Option A

4. Quick Check:

   Correct parameter order = D [OK]

Hint: Remember: original string first, then old, then new substring [OK]

Common Mistakes:

• Swapping old and new substring positions
• Putting new substring before old substring
• Confusing parameter order

3. Given the SQL query:
SELECT REPLACE('banana', 'a', 'o');
What is the output?

medium

A. 'bnn'

B. 'banana'

C. 'bonono'

D. 'banano'

Solution

1. Step 1: Identify the string and substrings

   The original string is 'banana'. We replace all 'a' with 'o'.

2. Step 2: Replace all 'a' with 'o'

   Replacing each 'a' in 'banana' results in 'bonono'.

3. Final Answer:

   'bonono' -> Option C

4. Quick Check:

   All 'a' replaced by 'o' = 'bonono' [OK]

Hint: Replace every target letter, not just first [OK]

Common Mistakes:

• Replacing only first occurrence
• Not replacing any character
• Removing characters instead of replacing

4. What is wrong with this SQL query?
SELECT REPLACE('hello world', 'l');

medium

A. It is missing the new substring to replace with.

B. The string to search in is missing.

C. The REPLACE function cannot be used in SELECT statements.

D. The function should be written as REPLACE('l', 'hello world').

Solution

1. Step 1: Check REPLACE function parameters

   REPLACE requires three parameters: original string, old substring, new substring.

2. Step 2: Identify missing parameter

   The query only has two parameters: original string and old substring. The new substring is missing.

3. Final Answer:

   It is missing the new substring to replace with. -> Option A

4. Quick Check:

   Missing third parameter = A [OK]

Hint: REPLACE needs 3 parameters: string, old, new [OK]

Common Mistakes:

• Using only two parameters
• Swapping parameter order
• Assuming REPLACE works with one substring only

5. You have a table products with a column description containing the text 'color' spelled as 'colour' in some rows. Which SQL query correctly updates all 'colour' to 'color' in the description column?

hard

A. UPDATE products SET description = REPLACE('colour', 'color', description);

B. UPDATE products SET description = REPLACE(description, 'colour', 'color');

C. UPDATE products SET description = REPLACE(description, 'color', 'colour');

D. UPDATE products SET description = REPLACE(description, 'colour');

Solution

1. Step 1: Understand the goal

   We want to replace all occurrences of 'colour' with 'color' in the description column.

2. Step 2: Check each query's correctness

   UPDATE products SET description = REPLACE(description, 'colour', 'color'); correctly uses REPLACE with the column first, then old substring 'colour', then new substring 'color'. UPDATE products SET description = REPLACE('colour', 'color', description); has wrong parameter order. UPDATE products SET description = REPLACE(description, 'color', 'colour'); replaces 'color' with 'colour' (opposite). UPDATE products SET description = REPLACE(description, 'colour'); misses the new substring parameter.

3. Final Answer:

   UPDATE products SET description = REPLACE(description, 'colour', 'color'); -> Option B

4. Quick Check:

   Correct update syntax with REPLACE = B [OK]

Hint: Use REPLACE(column, old, new) in UPDATE to fix text [OK]

Common Mistakes:

• Swapping old and new substrings
• Missing new substring parameter
• Using wrong parameter order