https://www.sqlteaching.com SQL练习网站
SELECT * FROM friends_of_pickles 返回所有行和列
SELECT name,gender FROM friends_of_pickles 返回name,gender的所有行和列
SELECT * FROM friends_of_pickles WHERE species = 'dog'; 返回 species为dog的所有行和列
SELECT * FROM friends_of_pickles WHERE height_cm < 45; 返回height_cm小于45的所有行和列
SELECT * FROM friends_of_pickles WHERE height_cm >= 45; 返回height_cm大于等于45的所有行和列
SELECT * FROM friends_of_pickles WHERE height_cm >= 45 AND species= 'human'; 返回height_cm大于等于45并且species=human的所有行和列
SELECT * FROM friends_of_pickles WHERE height_cm >= 45 OR species= 'human';返回height_cm大于等于45或者species=human的所有行和列
SELECT * FROM friends_of_pickles WHERE species IN ('human','dog'); 返回species在human,dog中的所有行和列
SELECT DISTINCT gender FROM friends_of_pickles WHERE species IN ('human','dog'); 返回species在human,dog中的物种的gender并去重
SELECT * FROM friends_of_pickles ORDER BY name 返回按name的升序排序所有的行和列
SELECT * FROM friends_of_pickles ORDER BY name DESC; 返回按name的降序排序所有的行和列
SELECT * FROM friends_of_pickles ORDER BY name DESC LIMIT 2; 返回按name的降序排序前两行的行和列
SELECT COUNT(*) FROM friends_of_pickles; 返回所有的行数
