How does Oracle count the total number of unique values?

In Oracle, the COUNT() function can be used to calculate the total number of different values. It is an SQL aggregate function used to calculate the number of rows in a selected column.

For example, if there is a table named “customers” with a column named “country”, you can use the following query to count the total number of different “country” values:

SELECT COUNT(DISTINCT country) FROM customers;

This will return the total number of distinct values in the “country” column.