ZINCRBY for score updates in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to increase the score of member 'player1' by 10 in the sorted set 'game_scores'.

Redis

ZINCRBY game_scores [1] player1

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

AINCRBY

Bplayer1

Cgame_scores

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the member name where the increment should be.

Using the key name instead of the increment.

The ZINCRBY command increases the score of a member by the specified increment. Here, 10 is the increment.

2fill in blank

medium

Complete the code to increase the score of member 'user42' by 5 in the sorted set 'leaderboard'.

Redis

ZINCRBY [1] 5 user42

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

A5

Bleaderboard

Cuser42

Dscoreboard

Attempts:

3 left

💡 Hint

Common Mistakes

Using the member name instead of the key name.

Confusing the increment value with the key.

The first argument after ZINCRBY is the key name of the sorted set, here 'leaderboard'.

3fill in blank

hard

Fix the error in the command to increase 'memberX' score by 3 in 'scores'.

Redis

ZINCRBY scores [1] memberX

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

AmemberX

Bscores

C3

DINCR

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the member name where the increment should be.

Using a keyword instead of a number.

The increment must be a number, here 3, not the member name or other keywords.

4fill in blank

hard

Fill both blanks to increase 'alice' score by 7 in the sorted set 'players'.

Redis

ZINCRBY [1] [2] alice

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

Aplayers

B7

C7.0

Dplayer_scores

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the key and increment.

Using a float number instead of an integer.

The first blank is the key name 'players'. The second blank is the increment '7'.

5fill in blank

hard

Fill all three blanks to increase the score of 'bob' by 4.5 in the sorted set 'game_rankings'.

Redis

ZINCRBY [1] [2] [3]

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

Agame_rankings

B4.5

Cbob

Drankings

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of arguments.

Using an integer instead of a decimal when decimal is needed.

The command syntax is: ZINCRBY key increment member. Here, key='game_rankings', increment='4.5', member='bob'.

Practice

1.

What does the Redis command ZINCRBY do?

easy

A. It creates a new sorted set without any members.

B. It increases the score of a member in a sorted set by a given amount.

C. It returns the rank of a member in a sorted set.

D. It deletes a member from a sorted set.

Solution

1. Step 1: Understand the purpose of ZINCRBY

   ZINCRBY is used to increase the score of a member in a sorted set by a specified increment.

2. Step 2: Compare with other options

   Other options describe different commands: deletion, rank retrieval, or creation, which are not what ZINCRBY does.

3. Final Answer:

   It increases the score of a member in a sorted set by a given amount. -> Option B

4. Quick Check:

   ZINCRBY increments score of member [OK]

Hint: ZINCRBY always adds to a member's score in sorted sets [OK]

Common Mistakes:

• Confusing ZINCRBY with ZREM (removal)
• Thinking it returns rank instead of updating score
• Assuming it creates a new sorted set without members

2.

Which of the following is the correct syntax to increase the score of member user1 by 5 in sorted set leaderboard?

?

easy

A. ZINCRBY leaderboard 5 user1

B. ZINCRBY leaderboard user1 5

C. ZINCRBY 5 leaderboard user1

D. ZINCRBY user1 leaderboard 5

Solution

1. Step 1: Recall ZINCRBY syntax

   The correct syntax is: ZINCRBY key increment member.

2. Step 2: Match syntax with options

   ZINCRBY leaderboard 5 user1 matches the correct order: ZINCRBY leaderboard 5 user1.

3. Final Answer:

   ZINCRBY leaderboard 5 user1 -> Option A

4. Quick Check:

   Command order = ZINCRBY key increment member [OK]

Hint: Remember: ZINCRBY key increment member [OK]

Common Mistakes:

• Swapping member and increment positions
• Putting member before key
• Using increment before key

3.

Given the following Redis commands executed in order:

ZINCRBY scores 10 alice
ZINCRBY scores 5 bob
ZINCRBY scores -3 alice
ZINCRBY scores 2 charlie

What is the score of alice after these commands?

medium

A. 7

B. 10

C. 12

D. -3

Solution

1. Step 1: Calculate alice's score changes

   First increment: +10, then decrement: -3, total = 10 - 3 = 7.

2. Step 2: Confirm final score

   Other members' scores do not affect alice's score.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   10 - 3 = 7 [OK]

Hint: Add increments for the same member to get final score [OK]

Common Mistakes:

• Ignoring negative increments
• Adding scores of other members
• Using only the first increment

4.

What is wrong with this Redis command to increase user2's score by 4 in sorted set game_scores?

ZINCRBY game_scores user2 4

medium

A. The increment value must be negative.

B. The key name is missing.

C. The command should be ZADD instead of ZINCRBY.

D. The increment and member arguments are swapped.

Solution

1. Step 1: Check argument order for ZINCRBY

   ZINCRBY syntax is: ZINCRBY key increment member. Here, 'user2' and '4' are swapped.

2. Step 2: Identify the error

   The command should be: ZINCRBY game_scores 4 user2.

3. Final Answer:

   The increment and member arguments are swapped. -> Option D

4. Quick Check:

   Order must be key, increment, member [OK]

Hint: Increment always comes before member in ZINCRBY [OK]

Common Mistakes:

• Swapping increment and member
• Using ZADD instead of ZINCRBY for increment
• Thinking increment must be negative

5.

You have a sorted set ranking with members and scores:

"alice" 15
"bob" 20
"carol" 10

You want to increase carol's score by 12 and decrease bob's score by 5 using Redis commands. Which sequence of commands correctly updates the scores?

hard

A. ZADD ranking 22 carol
ZADD ranking 15 bob

B. ZINCRBY ranking carol 12
ZINCRBY ranking bob -5

C. ZINCRBY ranking 12 carol
ZINCRBY ranking -5 bob

D. ZINCRBY ranking 5 carol
ZINCRBY ranking -12 bob

Solution

1. Step 1: Apply correct ZINCRBY syntax for increments

   To increase carol's score by 12: ZINCRBY ranking 12 carol.

2. Step 2: Apply correct ZINCRBY syntax for decrement

   To decrease bob's score by 5: ZINCRBY ranking -5 bob.

3. Step 3: Verify other options

   ZINCRBY ranking carol 12 ZINCRBY ranking bob -5 swaps increment and member, ZADD ranking 22 carol ZADD ranking 15 bob uses ZADD which replaces scores, ZINCRBY ranking 5 carol ZINCRBY ranking -12 bob uses wrong increments.

4. Final Answer:

   ZINCRBY ranking 12 carol ZINCRBY ranking -5 bob -> Option C

5. Quick Check:

   Use ZINCRBY with positive and negative increments [OK]

Hint: Use positive or negative increments with ZINCRBY to adjust scores [OK]

Common Mistakes:

• Swapping member and increment arguments
• Using ZADD which overwrites scores instead of incrementing
• Using wrong increment values