SQL Count

A commonly used aggregate function in SQL is COUNT. COUNT returns the number of rows that match the given criteria.

COUNT(*)

If we only want to see how many records are in a table (but not actually view those records), we could use COUNT(*). COUNT(*) returns everything - including null values and duplicates.

SQL statement

SELECT COUNT(*) FROM Individual

Source Table

Result

COUNT(column name)

If we want to see how many non-null values are in a given column, we use COUNT(column name) where column name is the name of the column we want to test.

SQL statement

SELECT COUNT(LastName) FROM Individual

Source Table

Result

Combining COUNT & DISTINCT

If we only want to see how many unique names are in the table, we could nest the DISTINCT inside a COUNT function.

SQL statement

SELECT COUNT(DISTINCT(FirstName)) FROM Individual

Result

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