UPPER, LOWER, INITCAP in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert the column 'name' to uppercase.

PostgreSQL

SELECT [1](name) FROM employees;

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

ATRIM

BUPPER

CINITCAP

DLOWER

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOWER instead of UPPER will convert text to lowercase.

Using INITCAP capitalizes only the first letter of each word.

The UPPER function converts all letters in the string to uppercase.

2fill in blank

medium

Complete the code to convert the column 'city' to lowercase.

PostgreSQL

SELECT [1](city) FROM locations;

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

AINITCAP

BLTRIM

CLOWER

DUPPER

Attempts:

3 left

💡 Hint

Common Mistakes

Using UPPER will convert text to uppercase, not lowercase.

INITCAP capitalizes the first letter of each word, not all letters.

The LOWER function converts all letters in the string to lowercase.

3fill in blank

hard

Fix the error in the code to capitalize the first letter of each word in 'title'.

PostgreSQL

SELECT [1](title) FROM books;

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

ARTRIM

BUPPER

CLOWER

DINITCAP

Attempts:

3 left

💡 Hint

Common Mistakes

Using UPPER capitalizes all letters, not just the first letter of each word.

Using LOWER converts all letters to lowercase.

The INITCAP function capitalizes the first letter of each word in the string.

4fill in blank

hard

Fill both blanks to convert 'description' to lowercase and trim spaces from the right.

PostgreSQL

SELECT [1]([2](description)) FROM products;

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

ARTRIM

BLOWER

CUPPER

DINITCAP

Attempts:

3 left

💡 Hint

Common Mistakes

Using UPPER instead of LOWER changes text to uppercase.

Using LTRIM removes spaces from the left, not the right.

First, LOWER converts text to lowercase, then RTRIM removes trailing spaces.

5fill in blank

hard

Fill all three blanks to convert 'author' to uppercase, trim spaces from the left, and capitalize the first letter of each word.

PostgreSQL

SELECT [1]([2]([3](author))) FROM writers;

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

AINITCAP

BLTRIM

CUPPER

DLOWER

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing the order of functions causes unexpected results.

Using LOWER instead of UPPER changes text to lowercase.

The order is: first capitalize each word with INITCAP, then remove left spaces with LTRIM, and finally convert all letters to uppercase with UPPER.

Practice

1. What does the UPPER function do to a text string in PostgreSQL?

easy

A. Reverses the string

B. Converts all letters to lowercase

C. Capitalizes only the first letter of the string

D. Converts all letters to uppercase

Solution

1. Step 1: Understand the UPPER function

   The UPPER function changes every letter in the input text to its uppercase form.

2. Step 2: Compare with other options

   LOWER converts to lowercase, INITCAP capitalizes first letters, reversing is unrelated.

3. Final Answer:

   Converts all letters to uppercase -> Option D

4. Quick Check:

   UPPER = all uppercase [OK]

Hint: UPPER means all letters become capital [OK]

Common Mistakes:

• Confusing UPPER with LOWER
• Thinking INITCAP only changes first letter of whole string
• Assuming UPPER reverses text

2. Which of the following is the correct syntax to convert the column name to lowercase in PostgreSQL?

easy

A. SELECT LOWER name FROM table;

B. SELECT LOWER(name);

C. SELECT LOWER(name) FROM table;

D. SELECT name.LOWER() FROM table;

Solution

1. Step 1: Check function call syntax

   In PostgreSQL, functions are called with parentheses around arguments, e.g., LOWER(name).

2. Step 2: Validate full query syntax

   SELECT LOWER(name) FROM table; correctly uses SELECT LOWER(name) FROM table; which is valid SQL syntax.

3. Final Answer:

   SELECT LOWER(name) FROM table; -> Option C

4. Quick Check:

   Function call syntax = LOWER(name) [OK]

Hint: Use parentheses for functions: LOWER(column) [OK]

Common Mistakes:

• Omitting parentheses after function name
• Using dot notation like name.LOWER() which is invalid
• Missing FROM clause in query

3. Given a table users with a column fullname containing 'john DOE', what is the output of the query SELECT INITCAP(fullname) FROM users;?

medium

A. 'John Doe'

B. 'John DOE'

C. 'John doe'

D. 'JOHN DOE'

Solution

1. Step 1: Understand INITCAP behavior

   INITCAP capitalizes the first letter of each word and makes the rest lowercase.

2. Step 2: Apply to 'john DOE'

   It converts 'john' to 'John' and 'DOE' to 'Doe'.

3. Final Answer:

   'John Doe' -> Option A

4. Quick Check:

   INITCAP('john DOE') = 'John Doe' [OK]

Hint: INITCAP capitalizes first letter of each word [OK]

Common Mistakes:

• Assuming INITCAP only changes first word
• Thinking it keeps uppercase letters as is
• Confusing with UPPER or LOWER functions

4. Identify the error in this query: SELECT INITCAP fullname FROM employees;

medium

A. Column name should be uppercase

B. Missing parentheses around column name

C. Missing FROM clause

D. INITCAP is not a valid function

Solution

1. Step 1: Check function syntax

   Functions require parentheses around their arguments, so INITCAP should be called as INITCAP(fullname).

2. Step 2: Verify other parts

   FROM clause is present, INITCAP is valid, column case does not matter.

3. Final Answer:

   Missing parentheses around column name -> Option B

4. Quick Check:

   Function call needs parentheses [OK]

Hint: Always use parentheses with functions [OK]

Common Mistakes:

• Omitting parentheses for function calls
• Thinking column names must be uppercase
• Confusing missing FROM clause error

5. You want to display a list of product names from the products table where each word in the product name starts with a capital letter, but the rest of the letters are lowercase. Which query achieves this?

hard

A. SELECT INITCAP(product_name) FROM products;

B. SELECT UPPER(product_name) FROM products;

C. SELECT LOWER(product_name) FROM products;

D. SELECT CONCAT(UPPER(SUBSTRING(product_name,1,1)), LOWER(SUBSTRING(product_name,2))) FROM products;

Solution

1. Step 1: Understand the requirement

   Each word's first letter capitalized and rest lowercase matches INITCAP behavior.

2. Step 2: Evaluate options

   The INITCAP option does exactly this. The UPPER option makes all uppercase, the LOWER option makes all lowercase, the CONCAT option only capitalizes first letter of whole string.

3. Final Answer:

   SELECT INITCAP(product_name) FROM products; -> Option A

4. Quick Check:

   INITCAP = capitalized words [OK]

Hint: Use INITCAP for capitalizing each word [OK]

Common Mistakes:

• Using UPPER or LOWER instead of INITCAP
• Trying to manually concatenate substrings for each word
• Assuming INITCAP only affects first word