SUBSTRING and LEFT/RIGHT in MySQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to extract the first 3 characters from the column 'name'.

MySQL

SELECT [1](name, 3) AS first_three FROM users;

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ALEFT

BRIGHT

CSUBSTRING

DMID

Attempts:

3 left

💡 Hint

Common Mistakes

Using RIGHT instead of LEFT extracts characters from the end.

Using SUBSTRING without specifying the start position correctly.

The LEFT function extracts a specified number of characters from the start (left) of a string.

2fill in blank

medium

Complete the code to extract 4 characters starting from the 2nd character in 'description'.

MySQL

SELECT [1](description, 2, 4) AS part_desc FROM products;

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AMID

BLEFT

CSUBSTRING

DRIGHT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LEFT or RIGHT which do not allow specifying start position.

Confusing the order of parameters.

The SUBSTRING function extracts characters starting at a specific position for a given length.

3fill in blank

hard

Fix the error in the code to get the last 5 characters of 'filename'.

MySQL

SELECT [1](filename, 5) AS last_five FROM files;

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ARIGHT

BSUBSTRING

CLEFT

DMID

Attempts:

3 left

💡 Hint

Common Mistakes

Using LEFT extracts from the start, not the end.

Using SUBSTRING without calculating start position for the end.

The RIGHT function extracts characters from the end (right) of a string.

4fill in blank

hard

Fill both blanks to extract 3 characters starting from the 4th character of 'address'.

MySQL

SELECT [1](address, [2], 3) AS part_address FROM locations;

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ASUBSTRING

BLEFT

C4

DRIGHT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LEFT or RIGHT which do not take start position.

Using wrong start position number.

Use SUBSTRING with start position 4 to get 3 characters starting from the 4th character.

5fill in blank

hard

Fill both blanks to extract the first 2 characters of 'code' in uppercase.

MySQL

SELECT UPPER([1](code, [2])) AS code_start FROM codes;

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ALEFT

B2

CSUBSTRING

DRIGHT

Attempts:

3 left

💡 Hint

Common Mistakes

Using RIGHT extracts from end, not start.

Using SUBSTRING without correct parameters.

Use LEFT to get first 2 characters, then UPPER to convert to uppercase.

Practice

1. What does the MySQL function LEFT('Hello World', 5) return?

easy

A. 'World'

B. 'Hello'

C. 'Hello World'

D. 'WorldHello'

Solution

1. Step 1: Understand LEFT function

   The LEFT function extracts a specified number of characters from the start (left side) of a string.

2. Step 2: Apply LEFT to 'Hello World'

   Extracting 5 characters from the start of 'Hello World' gives 'Hello'.

3. Final Answer:

   'Hello' -> Option B

4. Quick Check:

   LEFT('Hello World', 5) = 'Hello' [OK]

Hint: LEFT gets characters from the start of the string [OK]

Common Mistakes:

• Confusing LEFT with RIGHT function
• Expecting the whole string instead of part
• Using wrong number of characters

2. Which of the following is the correct syntax to extract 3 characters starting from the 2nd character in MySQL?

easy

A. RIGHT('abcdef', 2, 3)

B. LEFT('abcdef', 2, 3)

C. SUBSTRING('abcdef', 2, 3)

D. SUBSTRING('abcdef', 3, 2)

Solution

1. Step 1: Recall SUBSTRING syntax

   SUBSTRING(string, start_position, length) extracts length characters starting at start_position.

2. Step 2: Check each option

   SUBSTRING('abcdef', 2, 3) uses SUBSTRING with start=2 and length=3, which is correct. LEFT and RIGHT do not accept three arguments.

3. Final Answer:

   SUBSTRING('abcdef', 2, 3) -> Option C

4. Quick Check:

   Correct SUBSTRING syntax = SUBSTRING('abcdef', 2, 3) [OK]

Hint: SUBSTRING needs start and length; LEFT/RIGHT only need length [OK]

Common Mistakes:

• Using LEFT or RIGHT with three arguments
• Swapping start and length values
• Starting count from zero instead of one

3. What is the result of this query?
SELECT SUBSTRING('Database', 5, 3) AS part1, LEFT('Database', 4) AS part2, RIGHT('Database', 2) AS part3;

medium

A. part1='bas', part2='Data', part3='se'

B. part1='base', part2='Data', part3='se'

C. part1='tab', part2='D', part3='se'

D. part1='bas', part2='Datab', part3='se'

Solution

1. Step 1: Calculate SUBSTRING('Database', 5, 3)

   Starting at position 5: 'D'(1), 'a'(2), 't'(3), 'a'(4), 'b'(5), 'a'(6), 's'(7), 'e'(8). Characters 5 to 7 are 'b', 'a', 's' -> 'bas'.

2. Step 2: Calculate LEFT('Database', 4) and RIGHT('Database', 2)

   LEFT takes first 4 chars: 'D', 'a', 't', 'a' -> 'Data'. RIGHT takes last 2 chars: 's', 'e' -> 'se'.

3. Final Answer:

   part1='bas', part2='Data', part3='se' -> Option A

4. Quick Check:

   SUBSTRING, LEFT, RIGHT results match part1='bas', part2='Data', part3='se' [OK]

Hint: Count characters carefully starting at 1 for SUBSTRING [OK]

Common Mistakes:

• Counting start position from zero
• Mixing up LEFT and RIGHT results
• Extracting wrong substring length

4. Identify the error in this query:
SELECT LEFT('Example', 3, 2) AS result;

medium

A. LEFT function does not accept three arguments

B. String 'Example' is too short

C. Missing FROM clause

D. RIGHT function should be used instead

Solution

1. Step 1: Check LEFT function syntax

   LEFT(string, length) accepts only two arguments: the string and number of characters from the left.

2. Step 2: Analyze the query

   The query uses three arguments in LEFT, which is invalid syntax and causes an error.

3. Final Answer:

   LEFT function does not accept three arguments -> Option A

4. Quick Check:

   LEFT syntax error = LEFT function does not accept three arguments [OK]

Hint: LEFT only needs string and length, no extra arguments [OK]

Common Mistakes:

• Adding extra arguments to LEFT or RIGHT
• Confusing LEFT with SUBSTRING syntax
• Ignoring syntax errors in function calls

5. You have a column full_name with values like 'John Smith'. Which query extracts the last 5 characters of full_name to get the last name part using MySQL functions?

hard

A. SELECT SUBSTRING(full_name, 6, 5) AS last_name FROM users;

B. SELECT LEFT(full_name, 5) AS last_name FROM users;

C. SELECT SUBSTRING(full_name, -5) AS last_name FROM users;

D. SELECT RIGHT(full_name, 5) AS last_name FROM users;

Solution

1. Step 1: Understand the requirement

   We want the last 5 characters of the full_name, which is the last name part 'Smith' in 'John Smith'.

2. Step 2: Choose the correct function

   RIGHT(string, length) extracts characters from the end. RIGHT(full_name, 5) returns last 5 characters.

3. Step 3: Check other options

   LEFT extracts from start, SUBSTRING with negative start is invalid in MySQL, and SUBSTRING with fixed start 6 may fail if names vary.

4. Final Answer:

   SELECT RIGHT(full_name, 5) AS last_name FROM users; -> Option D

5. Quick Check:

   RIGHT gets last characters = SELECT RIGHT(full_name, 5) AS last_name FROM users; [OK]

Hint: Use RIGHT to get characters from the end of a string [OK]

Common Mistakes:

• Using LEFT instead of RIGHT for last characters
• Using SUBSTRING with negative start (not supported)
• Assuming fixed position for last name