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cardinality

1. CARDINALITY Function​

The CARDINALITY function in H2 database is used to determine the number of elements in an array or a multiset.

2. Syntax​

The syntax for the CARDINALITY function in H2 database is as follows:

CARDINALITY(array_expression)

Arguments​

  • array_expression: The array or multiset for which the cardinality needs to be calculated.

Return​

  • The CARDINALITY function returns the number of elements in the given array or multiset.

3. Notes​

  • The CARDINALITY function in H2 database only supports arrays and multisets. It does not support other data types.
  • If the input array or multiset is NULL, the CARDINALITY function will return NULL.
  • If the input array or multiset is an empty collection, the CARDINALITY function will return 0.
  • Make sure to provide a valid array or multiset expression to the CARDINALITY function to avoid errors.

4. Examples​

Here are a few examples demonstrating the usage of the CARDINALITY function in H2 database:

Example 1 - Calculating the cardinality of an array:​

SELECT CARDINALITY(ARRAY[1, 2, 3, 4, 5]) AS count;

Output:

count
-----
5

Example 2 - Calculating the cardinality of a multiset:​

SELECT CARDINALITY(MULTISET[1, 2, 2, 3, 3, 3]) AS count;

Output:

count
-----
6

Example 3 - Calculating the cardinality of an empty array:​

SELECT CARDINALITY(ARRAY[]) AS count;

Output:

count
-----
0

There are no related functions specifically related to the CARDINALITY function in H2 database.