CASE in PL/pgSQL in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a CASE expression in PL/pgSQL.

PostgreSQL

DECLARE
  grade CHAR := 'B';
  result TEXT;
BEGIN
  result := CASE [1]
    WHEN 'A' THEN 'Excellent'
    WHEN 'B' THEN 'Good'
    ELSE 'Average'
  END;
END;

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ACHAR

Bresult

Cgrade

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Using the variable that stores the result instead of the grade.

Using the data type name instead of a variable.

The CASE expression evaluates the variable grade to decide the result.

2fill in blank

medium

Complete the code to use CASE without an expression (searched CASE) in PL/pgSQL.

PostgreSQL

DECLARE
  score INT := 75;
  result TEXT;
BEGIN
  result := CASE
    WHEN score >= [1] THEN 'Pass'
    ELSE 'Fail'
  END;
END;

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A50

B90

C100

D60

Attempts:

3 left

💡 Hint

Common Mistakes

Using a passing score that is too high like 90 or 100.

Confusing the comparison operator.

The searched CASE checks if score is greater or equal to 50 to pass.

3fill in blank

hard

Fix the error in the CASE expression by completing the missing keyword.

PostgreSQL

DECLARE
  day INT := 3;
  day_name TEXT;
BEGIN
  day_name := CASE day
    [1] 1 THEN 'Monday'
    WHEN 2 THEN 'Tuesday'
    ELSE 'Other'
  END;
END;

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ATHEN

BWHEN

CELSE

DIF

Attempts:

3 left

💡 Hint

Common Mistakes

Using IF instead of WHEN inside CASE.

Omitting the WHEN keyword causes syntax errors.

Each condition in a CASE expression must start with the WHEN keyword.

4fill in blank

hard

Fill both blanks to complete the searched CASE expression that categorizes age.

PostgreSQL

DECLARE
  age INT := 25;
  category TEXT;
BEGIN
  category := CASE
    WHEN age [1] 18 THEN 'Minor'
    WHEN age [2] 18 THEN 'Adult'
    ELSE 'Senior'
  END;
END;

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A<

B>=

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators that invert the logic.

Mixing up greater than and less than signs.

The first condition checks if age is less than 18 for 'Minor'. The second checks if age is greater or equal to 18 for 'Adult'.

5fill in blank

hard

Fill all three blanks to complete the CASE expression that assigns a letter grade based on score.

PostgreSQL

DECLARE
  score INT := 85;
  grade CHAR;
BEGIN
  grade := CASE
    WHEN score [1] 90 THEN 'A'
    WHEN score [2] 80 THEN 'B'
    ELSE [3]
  END;
END;

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A>=

B<

C'C'

D'B'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators that cause wrong grade assignment.

Putting the wrong letter grade in the ELSE clause.

The CASE assigns 'A' if score is 90 or more, 'B' if score is 80 or more, else 'C'.