SUNIONSTORE for storing results in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to store the union of sets 'set1' and 'set2' into 'resultSet'.

Redis

SUNIONSTORE [1] set1 set2

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

AresultSet

Bset1

Cset2

DunionSet

Attempts:

3 left

💡 Hint

Common Mistakes

Using one of the source sets as the destination, which overwrites original data.

Forgetting to specify the destination key.

The SUNIONSTORE command stores the union of the given sets into the specified destination key. Here, 'resultSet' is the destination.

2fill in blank

medium

Complete the code to store the union of 'usersOnline' and 'usersActive' into 'allUsers'.

Redis

SUNIONSTORE [1] usersOnline usersActive

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

AusersOnline

BactiveOnline

CusersActive

DallUsers

Attempts:

3 left

💡 Hint

Common Mistakes

Using one of the source keys as the destination, causing data loss.

Choosing a destination key that does not clearly represent the union.

The destination key 'allUsers' will hold the union of 'usersOnline' and 'usersActive'.

3fill in blank

hard

Fix the error in the command to store the union of 'setA' and 'setB' into 'unionSet'.

Redis

SUNIONSTORE setA [1] setB

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

AunionSet

BsetB

CsetA

DresultSet

Attempts:

3 left

💡 Hint

Common Mistakes

Placing the destination key in the wrong position.

Using a source set as the destination key.

The first argument after SUNIONSTORE must be the destination key. Here, 'unionSet' is the correct destination to store the union.

4fill in blank

hard

Fill both blanks to store the union of 'group1' and 'group2' into 'combinedGroup'.

Redis

SUNIONSTORE [1] [2] group2

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

AcombinedGroup

Bgroup1

Cgroup2

DunionGroup

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the destination and source keys.

Using the same key for destination and source.

The first blank is the destination key 'combinedGroup'. The second blank is the first source set 'group1'. The command stores the union of 'group1' and 'group2' into 'combinedGroup'.

5fill in blank

hard

Fill all three blanks to store the union of 'teamA', 'teamB', and 'teamC' into 'allTeams'.

Redis

SUNIONSTORE [1] [2] [3] teamC

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

AallTeams

BteamA

CteamB

DcombinedTeams

Attempts:

3 left

💡 Hint

Common Mistakes

Using source keys as the destination.

Incorrect order of source sets.

The first blank is the destination key 'allTeams'. The second and third blanks are the first two source sets 'teamA' and 'teamB'. The command unions 'teamA', 'teamB', and 'teamC' into 'allTeams'.

Practice

1. What does the Redis command SUNIONSTORE destination key1 key2 do?

easy

A. It merges the sets stored at key1 and key2 and stores the result in destination.

B. It deletes the sets at key1 and key2 and creates a new set at destination.

C. It returns the union of sets at key1 and key2 without storing it.

D. It copies the set at key1 to destination without merging.

Solution

1. Step 1: Understand SUNIONSTORE purpose

   The command merges multiple sets into one combined set.

2. Step 2: Identify storage behavior

   The result is stored in the specified destination key, overwriting if it exists.

3. Final Answer:

   It merges the sets stored at key1 and key2 and stores the result in destination. -> Option A

4. Quick Check:

   SUNIONSTORE merges and stores = C [OK]

Hint: SUNIONSTORE merges sets and saves result in destination [OK]

Common Mistakes:

• Confusing SUNIONSTORE with SUNION (which does not store)
• Thinking it deletes original sets
• Assuming it copies only one set

2. Which of the following is the correct syntax to store the union of sets setA and setB into resultSet using Redis?

easy

A. SUNIONSTORE setA setB resultSet

B. SUNIONSTORE resultSet setA setB

C. SUNION resultSet setA setB

D. SUNIONSTORE setA resultSet setB

Solution

1. Step 1: Recall SUNIONSTORE syntax

   The correct syntax is SUNIONSTORE destination key1 key2 ....

2. Step 2: Match keys to syntax

   Here, resultSet is destination, followed by sets setA and setB.

3. Final Answer:

   SUNIONSTORE resultSet setA setB -> Option B

4. Quick Check:

   Destination first, then sets = A [OK]

Hint: Destination key comes first in SUNIONSTORE command [OK]

Common Mistakes:

• Placing destination key last
• Using SUNION instead of SUNIONSTORE for storing
• Mixing order of keys

3. You have three sets:
setX = {1, 2, 3}
setY = {3, 4, 5}
setZ = {5, 6}
You want to create a new set combined that contains the union of all three sets. Which command correctly does this and stores the result in combined?

easy

A. SUNIONSTORE combined setX setY setZ

B. SUNIONSTORE combined setX setY

C. SUNION combined setX setY setZ

D. SUNIONSTORE setX setY setZ combined

Solution

1. Step 1: Recall SUNIONSTORE usage for multiple sets

   SUNIONSTORE can take multiple keys after the destination key.

2. Step 2: Verify correct order and keys

   Destination is combined, followed by setX, setY, and setZ.

3. Final Answer:

   SUNIONSTORE combined setX setY setZ -> Option A

4. Quick Check:

   Destination first, then all sets = B [OK]

Hint: List all sets after destination in SUNIONSTORE [OK]

Common Mistakes:

• Using SUNION instead of SUNIONSTORE to store
• Placing destination key last
• Omitting one or more sets

4. Given the following Redis sets:
SADD set1 a b c
SADD set2 b c d
What will be the members of resultSet after executing SUNIONSTORE resultSet set1 set2?

medium

A. ["a", "d"]

B. ["a", "b", "c"]

C. ["a", "b", "c", "d"]

D. ["b", "c", "d"]

Solution

1. Step 1: Identify members of each set

   set1 has {a, b, c}, set2 has {b, c, d}.

2. Step 2: Compute union of both sets

   The union is {a, b, c, d} combining all unique members.

3. Final Answer:

   ["a", "b", "c", "d"] -> Option C

4. Quick Check:

   Union of set1 and set2 = ["a", "b", "c", "d"] [OK]

Hint: Union combines all unique elements from both sets [OK]

Common Mistakes:

• Forgetting to include all unique elements
• Confusing union with intersection
• Assuming order matters in sets

5. You run the command SUNIONSTORE result set1 set2 but get an error. What is the most likely cause?

medium

A. SUNIONSTORE does not accept more than two sets.

B. You forgot to specify the destination key.

C. The sets set1 and set2 do not exist.

D. The key result already exists as a string, not a set.

Solution

1. Step 1: Understand data type requirements

   SUNIONSTORE requires the destination key to be a set or not exist.

2. Step 2: Identify error cause

   If result exists as a string or other type, Redis throws a type error.

3. Final Answer:

   The key result already exists as a string, not a set. -> Option D

4. Quick Check:

   Destination key type mismatch causes error [OK]

Hint: Destination key must be a set or not exist [OK]

Common Mistakes:

• Assuming missing keys cause errors (they don't)
• Thinking SUNIONSTORE limits number of sets
• Ignoring key data types