In Redis, the SCARD command returns the number of members in the specified set. This is referred to as the cardinality of the set.

Syntax

The syntax goes like this:

SCARD key

Where key is the key in question.

Example

Here’s an example of using SCARD against a set called animals:

SCARD animals

Result:

(integer) 4

The result is an integer reply of 4, which means the set contains four members.

We can verify this by looking at all the members in the set:

SMEMBERS animals

Result:

1) "Horse"
2) "Ant"
3) "Dog"
4) "Cat"

If we add more members to the set, SCARD returns a different number:

SADD animals "Cow" "Mouse" "Chicken"

Result:

(integer) 3

Now let’s run SCARD again to check the set’s cardinality:

SCARD animals

Result:

(integer) 7

When the Key Doesn’t Exist

If the key doesn’t exist, SCARD returns 0:

SCARD oops

Result:

(integer) 0

In this case, the key oops doesn’t exist, and we get an integer reply of zero.