How to Count Distinct Values in a SQL Column Without a Subquery?

Counting Distinct Values in a SQL Column

Problem:

Retrieving distinct values from a column using SELECT DISTINCT or GROUP BY is straightforward. However, how do we determine the count of these distinct values without resorting to a subquery?

Solution:

The DISTINCT keyword can be integrated within the COUNT aggregate function as follows:

SELECT COUNT(DISTINCT column_name) AS some_alias FROM table_name

Explanation:

The COUNT(DISTINCT column_name) expression computes the number of unique occurrences of the values in the specified column, providing a precise count of the distinct values. The alias "some_alias" serves to label the resulting column in the output.

By incorporating DISTINCT within the COUNT function, you eliminate duplicate values in the count, ensuring an accurate representation of the number of distinct elements in the column.

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