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ZSCORE

Introduction and Use Case(s)​

The ZSCORE command in Redis is used to retrieve the score associated with a member in a sorted set. This command is particularly useful in scenarios where you need to know the ranking or priority of an element within a collection, such as leaderboard applications, task scheduling systems, or any system implementing priority queues.

Syntax​

ZSCORE key member

Parameter Explanations​

  • key: The name of the sorted set where the member is stored.
  • member: The specific member whose score you want to retrieve.

Return Values​

  • If the member exists in the sorted set, the command returns its score as a string.
  • If the member does not exist, it returns nil.

Example Outputs:

  • Member exists: "3.14"
  • Member does not exist: (nil)

Code Examples​

dragonfly> ZADD myzset 1 "a"
(integer) 1
dragonfly> ZADD myzset 2 "b"
(integer) 1
dragonfly> ZADD myzset 3 "c"
(integer) 1
dragonfly> ZSCORE myzset "b"
"2"
dragonfly> ZSCORE myzset "d"
(nil)

Best Practices​

  • Ensure that the key you're querying actually exists and is a sorted set to avoid type errors.
  • Regularly monitor your sorted sets for outliers in scores that may indicate erroneous data.

Common Mistakes​

  • Attempting to use ZSCORE on a key that is not a sorted set will result in an error.
  • Querying for a member that doesn't exist in the specified sorted set will return nil, which should be handled appropriately in your application logic.

FAQs​

Q: What happens if the key does not exist? A: If the key does not exist, the command returns nil.

Q: Can scores be negative or floating-point numbers? A: Yes, scores in Redis sorted sets can be negative or floating-point numbers.