How to count the number of rows?

The COUNT function returns the number of rows in a query. The syntax for the COUNT function is:

SELECT COUNT (expression) 
FROM tables
WHERE predicates; 

For example, you might wish to know how many employees have a salary that is above $25,000 / year.

SELECT COUNT (*) as "Number of employees"
FROM employees
WHERE salary > 25000; 

In this example, we've aliased the count(*) field as "Number of employees". As a result, "Number of employees" will display as the field name when the result set is returned.

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