Recursive CTE concept in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a recursive CTE with the anchor member.

SQL

WITH RECURSIVE cte AS (SELECT [1] AS n)

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A1

Bn

C*

DCOUNT(*)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a column name instead of a constant for the anchor member.

Using an aggregate function in the anchor member.

The anchor member of a recursive CTE must provide a starting value. Here, we start with 1 as the initial number.

2fill in blank

medium

Complete the code to add the recursive member that increments the number by 1.

SQL

WITH RECURSIVE cte AS (SELECT 1 AS n UNION ALL SELECT n [1] 1 FROM cte WHERE n < 5)

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A/

B+

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to reference the CTE in the recursive member.

The recursive member adds 1 to the current number to generate the next number in the sequence.

3fill in blank

hard

Fix the error in the recursive CTE by completing the termination condition.

SQL

WITH RECURSIVE cte AS (SELECT 1 AS n UNION ALL SELECT n + 1 FROM cte WHERE n [1] 10) SELECT * FROM cte;

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A<=

B>

C=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' which stops recursion too early.

Using '=' which only allows one iteration.

The termination condition must allow recursion until n is less than or equal to 10 to include 10 in the results.

4fill in blank

hard

Fill both blanks to create a recursive CTE that generates even numbers up to 10.

SQL

WITH RECURSIVE evens AS (SELECT 2 AS num UNION ALL SELECT num [1] 2 FROM evens WHERE num [2] 10) SELECT * FROM evens;

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A+

B-

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction instead of addition.

Using a wrong comparison operator that excludes 10.

The recursive member adds 2 to generate even numbers, and the condition ensures numbers up to 10 are included.

5fill in blank

hard

Fill all three blanks to create a recursive CTE that calculates factorial of numbers from 1 to 5.

SQL

WITH RECURSIVE factorial AS (SELECT 1 AS n, 1 AS fact UNION ALL SELECT n [1] 1, fact [2] n FROM factorial WHERE n [3] 5) SELECT * FROM factorial;

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

A+

B*

C<=

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction instead of addition for n.

Using addition instead of multiplication for factorial.

Using wrong comparison operator that stops recursion too early.

The recursive CTE increments n by 1, multiplies fact by n, and continues until n is 5 to compute factorials.