Candidate key finding using closure in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to compute the closure of attribute set A under functional dependencies F.

DBMS Theory

closure = set(A)
changed = True
while changed:
    changed = False
    for (X, Y) in F:
        if set(X).issubset(closure) and not set(Y).issubset(closure):
            closure.update([1])
            changed = True

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

AF

BX

Cclosure

DY

Attempts:

3 left

💡 Hint

Common Mistakes

Adding X instead of Y to the closure.

Updating closure with the whole FD instead of Y.

The closure of A is expanded by adding attributes Y from functional dependencies X -> Y when X is a subset of the closure.

2fill in blank

medium

Complete the code to check if attribute set A is a candidate key by comparing its closure with all attributes R.

DBMS Theory

if closure == [1]:
    print("A is a candidate key")
else:
    print("A is not a candidate key")

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AR

BA

CF

Dclosure

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing closure with A or F instead of R.

Using assignment instead of equality check.

A candidate key's closure must include all attributes in the relation R.

3fill in blank

hard

Fix the error in the code that computes closure by replacing the incorrect operator.

DBMS Theory

closure = set(A)
for (X, Y) in F:
    if set(X) [1] closure:
        closure.update(Y)

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A==

B<=

C>

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using equality or inequality instead of subset check.

Using greater than operator which is incorrect.

To check if X is a subset of closure, use the subset operator <=.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps attribute sets to their closures.

DBMS Theory

closures = { [1]: compute_closure([2], F) for [1] in subsets(R)}

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AX

BF

CR

Dclosure

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variables for key and argument.

Using F or R incorrectly in place of the variable.

The comprehension iterates over subsets of R using variable X and computes closure for each X.

5fill in blank

hard

Fill all three blanks to filter candidate keys from all subsets by checking closure equality.

DBMS Theory

candidate_keys = [[1] for [2] in subsets(R) if compute_closure([2], F) == [3]]

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AX

Bsubset

CR

DF

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Comparing closure with F instead of R.

We iterate over subsets named subset, check if their closure equals R, and collect those subsets as candidate keys.