if/else logic in models in dbt - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new column status that shows 'active' if is_active is true, otherwise 'inactive'.

dbt

select user_id, case when is_active = [1] then 'active' else 'inactive' end as status from users

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

A'true'

Bfalse

C1

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around true like 'true' makes it a string, not a boolean.

Using false instead of true reverses the logic.

The case when checks if is_active is true to assign 'active'.

2fill in blank

medium

Complete the code to assign category as 'high' if score is greater than 80, else 'low'.

dbt

select user_id, case when score [1] 80 then 'high' else 'low' end as category from scores

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

A<=

B=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' checks for exact equality, not greater than.

Using '<=' or '<' reverses the intended logic.

The condition checks if score is greater than 80 to assign 'high'.

3fill in blank

hard

Fix the error in the code to correctly assign risk_level based on age: 'senior' if age >= 65, else 'adult'.

dbt

select user_id, case when age [1] 65 then 'senior' else 'adult' end as risk_level from demographics

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

A>=

B!=

C=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' assigns 'senior' to younger ages incorrectly.

Using '=' only matches exactly 65, missing older ages.

The condition must check if age is greater than or equal to 65 to assign 'senior'.

4fill in blank

hard

Fill both blanks to create a column discount that is 0.2 if purchase_amount is greater than 100, else 0.

dbt

select customer_id, case when purchase_amount [1] 100 then [2] else 0 end as discount from sales

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

A>

B<

C0.2

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' reverses the condition.

Using 1 instead of 0.2 assigns wrong discount.

The code checks if purchase_amount is greater than 100 to assign a 0.2 discount.

5fill in blank

hard

Fill all three blanks to create a column grade that is 'A' if score >= 90, 'B' if score >= 80, else 'C'.

dbt

select student_id, case when score [1] 90 then 'A' when score [2] 80 then 'B' else [3] end as grade from exams

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

A>=

B>

C'C'

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' excludes boundary scores like 90 or 80.

Not quoting 'C' makes it invalid as a string.

Both conditions use '>=' to include the boundary scores, and else assigns 'C'.

Practice

1. In dbt models, which SQL construct is commonly used to add if/else logic for creating new columns?

easy

A. WHILE LOOP

B. FOR LOOP

C. CASE WHEN ... THEN ... ELSE ... END

D. FUNCTION CALL

Solution

1. Step 1: Understand conditional logic in SQL

   SQL uses CASE statements to check conditions and return values accordingly.

2. Step 2: Identify the correct syntax for if/else logic

   CASE WHEN ... THEN ... ELSE ... END is the standard way to implement if/else logic in SQL and dbt models.

3. Final Answer:

   CASE WHEN ... THEN ... ELSE ... END -> Option C

4. Quick Check:

   CASE statement = if/else logic [OK]

Hint: Remember: CASE is SQL's if/else [OK]

Common Mistakes:

• Confusing loops with conditional logic
• Using function calls instead of CASE
• Trying to use procedural code in SQL

2. Which of the following is the correct syntax for a CASE statement in a dbt model to check if a column score is greater than 50?

easy

A. CASE WHEN score THEN 'Pass' ELSE 'Fail' END

B. CASE score > 50 THEN 'Pass' ELSE 'Fail'

C. IF score > 50 THEN 'Pass' ELSE 'Fail' END

D. CASE WHEN score > 50 THEN 'Pass' ELSE 'Fail' END

Solution

1. Step 1: Review correct CASE syntax

   The correct syntax starts with CASE WHEN condition THEN result ELSE other_result END.

2. Step 2: Check each option for syntax errors

   CASE WHEN score > 50 THEN 'Pass' ELSE 'Fail' END correctly uses CASE WHEN score > 50 THEN 'Pass' ELSE 'Fail' END. Others miss WHEN, END, or have wrong structure.

3. Final Answer:

   CASE WHEN score > 50 THEN 'Pass' ELSE 'Fail' END -> Option D

4. Quick Check:

   CASE WHEN + condition + THEN + result + ELSE + result + END [OK]

Hint: CASE must have WHEN and END keywords [OK]

Common Mistakes:

• Omitting WHEN keyword
• Missing END at the end
• Using IF instead of CASE in SQL

3. Given the following dbt model SQL snippet, what will be the value of status for a row where score = 75?

SELECT
  score,
  CASE
    WHEN score >= 90 THEN 'Excellent'
    WHEN score >= 70 THEN 'Good'
    ELSE 'Average'
  END AS status
FROM scores_table

medium

A. 'Good'

B. NULL

C. 'Average'

D. 'Excellent'

Solution

1. Step 1: Check conditions in order for score = 75

   First condition: score >= 90? No (75 < 90). Second condition: score >= 70? Yes (75 >= 70).

2. Step 2: Determine which condition applies first

   The first true condition is WHEN score >= 70 THEN 'Good', so status = 'Good'.

3. Final Answer:

   'Good' -> Option A

4. Quick Check:

   75 >= 70 = 'Good' [OK]

Hint: Check CASE conditions top to bottom [OK]

Common Mistakes:

• Ignoring order of CASE conditions
• Choosing 'Excellent' incorrectly
• Assuming ELSE applies before WHEN

4. Identify the error in this dbt model snippet:

SELECT
  user_id,
  CASE
    WHEN age > 18 THEN 'Adult'
    WHEN age <= 18 THEN 'Minor'
    ELSE 'Unknown'
FROM users

medium

A. Missing END keyword for CASE statement

B. Incorrect comparison operator in WHEN clauses

C. ELSE clause cannot be used in CASE

D. Missing comma after user_id

Solution

1. Step 1: Check CASE statement syntax

   CASE statements must end with END keyword to close the block.

2. Step 2: Verify presence of END keyword

   The snippet lacks END after ELSE 'Unknown', causing syntax error.

3. Final Answer:

   Missing END keyword for CASE statement -> Option A

4. Quick Check:

   CASE must end with END [OK]

Hint: Always close CASE with END [OK]

Common Mistakes:

• Forgetting END keyword
• Misplacing ELSE clause
• Assuming ELSE is optional

5. You want to create a new column category in your dbt model based on sales amount: if sales > 1000, category is 'High'; if sales between 500 and 1000 inclusive, category is 'Medium'; otherwise, 'Low'. Which CASE statement correctly implements this logic?

hard

A. CASE WHEN sales > 1000 THEN 'High' WHEN sales > 500 THEN 'Medium' ELSE 'Low' END

B. CASE WHEN sales > 1000 THEN 'High' WHEN sales >= 500 AND sales <= 1000 THEN 'Medium' ELSE 'Low' END

C. CASE WHEN sales > 500 AND sales <= 1000 THEN 'Medium' WHEN sales > 1000 THEN 'High' ELSE 'Low' END

D. CASE WHEN sales > 1000 THEN 'High' ELSE WHEN sales >= 500 THEN 'Medium' ELSE 'Low' END

Solution

1. Step 1: Analyze the conditions and their order

   Check sales > 1000 first for 'High', then sales between 500 and 1000 inclusive for 'Medium', else 'Low'.

2. Step 2: Verify correct syntax and condition order

   CASE WHEN sales > 1000 THEN 'High' WHEN sales >= 500 AND sales <= 1000 THEN 'Medium' ELSE 'Low' END correctly orders conditions (highest first) and uses proper inclusive range with AND. CASE WHEN sales > 500 AND sales <= 1000 THEN 'Medium' WHEN sales > 1000 THEN 'High' ELSE 'Low' END misses inclusive lower bound (sales=500 fails) and suboptimal order. CASE WHEN sales > 1000 THEN 'High' WHEN sales > 500 THEN 'Medium' ELSE 'Low' END misses inclusive lower bound. CASE WHEN sales > 1000 THEN 'High' ELSE WHEN sales >= 500 THEN 'Medium' ELSE 'Low' END has syntax error with ELSE WHEN.

3. Final Answer:

   CASE WHEN sales > 1000 THEN 'High' WHEN sales >= 500 AND sales <= 1000 THEN 'Medium' ELSE 'Low' END -> Option B

4. Quick Check:

   Order and range checks correct in CASE WHEN sales > 1000 THEN 'High' WHEN sales >= 500 AND sales <= 1000 THEN 'Medium' ELSE 'Low' END [OK]

Hint: Check ranges carefully and order conditions top-down [OK]

Common Mistakes:

• Wrong order of conditions causing misclassification
• Syntax error using ELSE WHEN instead of WHEN
• Missing inclusive range checks