mysql 其形怪句

1. SELECT (SELECT COUNT(*) FROM world.city) - COUNT(*) FROM world.city WHERE id < 5;

2.SELECT SUM(IF(color = 'blue',1,0)) AS blue, SUM(IF(color = 'red',1,0)) AS red FROM items;

3. SELECT COUNT(color = 'blue' OR NULL) AS blue, COUNT(color='red' OR NULL) as red FROM items;

4. SELECT film_id,description FROM sakila.film ORDER BY title LIMIT 50,5;如果在大表的情况下，可以这样优化

SELECT film.film_id,film.description FROM sakila.film INNER JOIN (SELECT film_id FROM sakila.film ORDER BY title LIMIT 50,5) AS lim USING(film_id);