DATABASE Study Notes

1. When NULL, print something else - IFNULL(column name, 'content')
2. Print date only - DATE_FORMAT(column name, '%Y-%m-%d')
3. Contains string - LIKE '%STRING%', (% is a wildcard)
4. Average - AVG(column)
5. Decimals - round(decimal) = rounds to an integer, round(decimal, digits) = prints rounded to that many digits
6. TRUNCATE function - just see this blog
7. Not-equal operator - <> (same as !=)
8. LIMIT a - print a rows from the start
9. LIMIT a b - print from row a+1 to row b
10. DATEDIFF(end, start): returns the DATE difference expressed in 'DAY'
11. DATESTAMPDIFF(unit, start, end): returns the DATE difference in the given unit
12. Remove duplicates: DISTINCT field name
13. number, DATE BETWEEN A AND B
14. LEFT(string, len): returns the string cut to len from the start
15. RIGHT(string, len): omitted

[SQL] The difference between WHERE and HAVING