Question

I have a DoB field. I want to categories/group all users based on their age into these groups:

1. <20
2. 20-25
3. 25-30
4. 30-35
5. 35-40
6. 40-50
7. >50

Answer 1

SELECT
    CASE
        WHEN age < 20 THEN 'Under 20'
        WHEN age BETWEEN 20 and 29 THEN '20 - 29'
        WHEN age BETWEEN 30 and 39 THEN '30 - 39'
        WHEN age BETWEEN 40 and 49 THEN '40 - 49'
        WHEN age BETWEEN 50 and 59 THEN '50 - 59'
        WHEN age BETWEEN 60 and 69 THEN '60 - 69'
        WHEN age BETWEEN 70 and 79 THEN '70 - 79'
        WHEN age >= 80 THEN 'Over 80'
        WHEN age IS NULL THEN 'Not Filled In (NULL)'
    END as age_range,
    COUNT(*) AS count    
    FROM (SELECT TIMESTAMPDIFF(YEAR, dob, CURDATE()) AS age FROM gamers) as derived    
    GROUP BY age_range    
    ORDER BY age_range