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## What is cardinality in SQL example?

In SQL, the cardinality of a column in a given table refers **to the number of unique values that appear in the table for that column**. So, remember that the cardinality is a number. For example, let’s say we have a table with a “Sex” column which has only two possible values of “Male” and “Female”.

## What is the cardinality in SQL?

In SQL (Structured Query Language), the term cardinality refers **to the uniqueness of data values contained in a particular column (attribute) of a database table**. The lower the cardinality, the more duplicated elements in a column.

## How do you determine cardinality?

To view the index cardinality, you use **the SHOW INDEXES command**. (*) scroll to the right of the output to view the index cardinality. In the output, the PRIMARY KEY for the orderNumber column shows the table has 326 unique values, while the customerNumer column only has 98 distinct values.

## What is the example of cardinality?

The cardinality of a set is **a measure of a set’s size**, meaning the number of elements in the set. For instance, the set A = { 1 , 2 , 4 } A = {1,2,4} A={1,2,4} has a cardinality of 3 for the three elements that are in it.

## What are high cardinality features?

What is high cardinality? … A categorical feature is said **to possess high cardinality when there are too many of these unique values**. One-Hot Encoding becomes a big problem in such a case since we have a separate column for each unique value (indicating its presence or absence) in the categorical variable.

## What is the cardinality rule?

Cardinality is the counting and quantity principle referring **to the understanding that the last number used to count a group of objects represents how many are in the group**. A student who must recount when asked how many candies are in the set that they just counted, may not understand the cardinality principle.