6.17. SQL Select Functions
6.17.1. Sum
SELECT SUM(experience)
FROM astronauts
WHERE agency = 'NASA';
6.17.2. Average
SELECT AVG(age)
FROM astronauts
WHERE agency = 'NASA';
6.17.3. Count
SELECT COUNT(id)
FROM astronauts
WHERE agency = 'NASA';
SELECT COUNT(DISTINCT agency)
FROM astronauts;
SELECT COUNT(DISTINCT mission_name)
FROM astronauts
WHERE agency = 'NASA';