Have you ever been investigating a table and wanted to find out how many records it contains with a simple SELECT COUNT(*) query, but the query took a long time to run? Or, if you wanted to find the number of distinct values in a column, but the query was slow?
Well, we now have an easier way to run this query.
A new function, called APPROX_COUNT_DISTINCT. This lets you find the approximate number of distinct values in a column.
It's called an approximate because it doesn't give you the exact number. But, the number is pretty close.
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SELECT COUNT(DISTINCT first_name)
FROM student;
SELECT APPROX_COUNT_DISTINCT(first_name)
FROM student;
The first query uses the actual COUNT function, and the second uses the new function. The second query should run a lot faster and get a number that is pretty close to the correct one.
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