SUNION, SINTER, SDIFF set operations in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get the union of sets 'set1' and 'set2'.

Redis

SUNION [1]

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

Aset1 set2

Bset1

Cset2

Dset3

Attempts:

3 left

💡 Hint

Common Mistakes

Using only one set name returns just that set's members.

Using commas instead of spaces between set names.

The SUNION command returns all unique members from both sets. You need to specify both set names separated by space.

2fill in blank

medium

Complete the code to find the intersection of sets 'fruits' and 'citrus'.

Redis

SINTER [1]

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

Afruits,citrus

Bfruits citrus

Cfruits

Dcitrus

Attempts:

3 left

💡 Hint

Common Mistakes

Using commas between set names causes syntax errors.

Providing only one set name returns that set's members.

SINTER returns members common to all given sets. The set names must be separated by spaces, not commas.

3fill in blank

hard

Fix the error in the code to get the difference of sets 'A' and 'B'.

Redis

SDIFF [1]

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

AA B

BB

CA

DA,B

Attempts:

3 left

💡 Hint

Common Mistakes

Using commas between set names causes errors.

Using only one set name returns that set's members.

SDIFF returns members in the first set that are not in the others. Set names must be separated by spaces, not commas.

4fill in blank

hard

Fill all three blanks to get the union of 'setX' and 'setY' and store it in 'resultSet'.

Redis

SUNIONSTORE [1] [2] [3]

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

AresultSet

BsetX

CsetY

DsetZ

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping destination and source sets.

Using a set name that doesn't exist.

SUNIONSTORE stores the union of given sets into the destination key. The first argument is the destination, followed by the sets.

5fill in blank

hard

Fill all three blanks to store the difference of 'set1' and 'set2' in 'diffSet'.

Redis

SDIFFSTORE [1] [2] [3]

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

AdiffSet

Bset1

Cset2

Dset3

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of arguments.

Using a wrong set name.

SDIFFSTORE stores the difference of the first set minus the others into the destination key. The order is destination, then sets.

Practice

1. What does the Redis command SUNION do when applied to multiple sets?

easy

A. It returns all unique elements from all given sets combined.

B. It returns only the elements common to all given sets.

C. It returns elements unique to the first set only.

D. It deletes all the given sets from the database.

Solution

1. Step 1: Understand SUNION operation

   The SUNION command merges all elements from the given sets and removes duplicates.

2. Step 2: Compare with other set operations

   SINTER returns only common elements, SDIFF returns unique elements from the first set, so SUNION is the only one that merges all uniquely.

3. Final Answer:

   It returns all unique elements from all given sets combined. -> Option A

4. Quick Check:

   SUNION = all unique elements combined [OK]

Hint: SUNION combines all sets without duplicates [OK]

Common Mistakes:

• Confusing SUNION with SINTER (common elements)
• Thinking SUNION returns only first set elements
• Assuming SUNION deletes sets

2. Which of the following is the correct syntax to find the intersection of two sets set1 and set2 in Redis?

easy

A. SINTER set1 set2

B. SUNION set1 set2

C. SDIFF set1 set2

D. SINTERSECTION set1 set2

Solution

1. Step 1: Recall Redis command for intersection

   The correct Redis command to find common elements is SINTER.

2. Step 2: Check syntax correctness

   The syntax is SINTER key1 key2 .... SINTER set1 set2 matches this exactly.

3. Final Answer:

   SINTER set1 set2 -> Option A

4. Quick Check:

   SINTER syntax = SINTER keys [OK]

Hint: Use SINTER for intersection syntax [OK]

Common Mistakes:

• Using SUNION instead of SINTER
• Using non-existent command SINTERSECTION
• Confusing SDIFF with intersection

3. Given the following Redis sets:
set1 = {"apple", "banana", "cherry"}
set2 = {"banana", "date", "fig"}
What is the result of SINTER set1 set2?

medium

A. ["apple", "banana", "cherry", "date", "fig"]

B. ["banana"]

C. ["apple", "cherry"]

D. ["date", "fig"]

Solution

1. Step 1: Identify common elements between set1 and set2

   Elements in set1: apple, banana, cherry; set2: banana, date, fig. The only common element is banana.

2. Step 2: Understand SINTER output

   SINTER returns only elements present in all sets, so the result is ["banana"].

3. Final Answer:

   ["banana"] -> Option B

4. Quick Check:

   SINTER common elements = ["banana"] [OK]

Hint: SINTER returns only common elements [OK]

Common Mistakes:

• Listing all elements instead of common ones
• Confusing SINTER with SUNION or SDIFF
• Including elements unique to one set

4. You run the command SDIFF set1 set2 but get an unexpected empty result. Given:
set1 = {"cat", "dog"}
set2 = {"cat", "dog", "mouse"}
What is the likely reason?

medium

A. set1 is empty, so SDIFF returns empty.

B. SDIFF syntax requires only one set argument.

C. Redis does not support SDIFF with these sets.

D. All elements of set1 are also in set2, so no unique elements remain.

Solution

1. Step 1: Understand SDIFF behavior

   SDIFF returns elements in the first set that are not in the other sets.

2. Step 2: Analyze given sets

   set1 has "cat" and "dog"; set2 has "cat", "dog", and "mouse". Since all set1 elements are in set2, SDIFF returns an empty set.

3. Final Answer:

   All elements of set1 are also in set2, so no unique elements remain. -> Option D

4. Quick Check:

   SDIFF unique first set elements = empty [OK]

Hint: SDIFF returns only unique first set elements [OK]

Common Mistakes:

• Assuming SDIFF requires only one set
• Thinking SDIFF returns common elements
• Believing Redis lacks SDIFF support

5. You have three Redis sets:
setA = {"red", "blue", "green"}
setB = {"blue", "yellow"}
setC = {"green", "yellow", "black"}
Which command returns elements that are in setA but not in setB or setC?

hard

A. SUNION setA setB setC

B. SINTER setA setB setC

C. SDIFF setA setB setC

D. SDIFF setB setA setC

Solution

1. Step 1: Understand SDIFF with multiple sets

   SDIFF returns elements in the first set that are not in any of the other sets.

2. Step 2: Apply SDIFF to given sets

   Elements in setA: red, blue, green. Elements in setB and setC combined: blue, yellow, green, black. Elements unique to setA are only "red".

3. Step 3: Verify command correctness

   SDIFF setA setB setC uses SDIFF with setA first, then setB and setC, which matches the requirement.

4. Final Answer:

   SDIFF setA setB setC -> Option C

5. Quick Check:

   SDIFF first set minus others = unique elements [OK]

Hint: Use SDIFF with first set then others to find unique elements [OK]

Common Mistakes:

• Using SINTER or SUNION instead of SDIFF
• Reversing set order in SDIFF
• Expecting SDIFF to return common elements