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Displaying posts with tag: row value expressions (reset)
Counting Distinct Records in SQL

The SQL language and its depths… Some of you readers might be aware of MySQL’s capability of counting distinct records through the COUNT() aggregate function. The MySQL documentation reads:

COUNT(DISTINCT expr,[expr...])

Returns a count of the number of rows with different non-NULL expr values.

In other words, you can count distinct first and last names very easily:

SELECT COUNT(DISTINCT FIRST_NAME, LAST_NAME)
FROM CUSTOMERS

That’s quite useful, but MySQL-specific ( …

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