如何从数据库中选择<select>语句？

-- 选择 id, name, age
SELECT id, name, age
FROM users;

-- 选择 id, name, age, city
SELECT id, name, age, city
FROM users
WHERE age > 25;

-- 分组查询，按 age 分组，每组只返回 age, name
SELECT age, name
FROM users
GROUP BY age;

-- 分组查询，按 age 分组，每组只返回 age, name, city
SELECT age, name, city
FROM users
GROUP BY age
HAVING city = 'New York';

-- 排序查询，按 age 降序，每组只返回 age, name
SELECT age, name
FROM users
GROUP BY age
ORDER BY age DESC;

-- 限制结果集的行数，每组只返回 age, name
SELECT age, name
FROM users
GROUP BY age
LIMIT 10;