此为自用
查询语句
1.select
SELECT column1,column2 FROM table1;常用的格式惯例：
大写了SELECT和FROM，而将表名和列名小写；
通常在列名中使用下划线，避免使用空格；
在每个语句末尾添加分号；
SQL不区分大小写。
2.limit
SELECT name,director FROM movies
LIMIT 15;3.order by
SELECT name, FROM,film_year,ticket_price FROM movies
ORDER BY film_year DESC,ticket_price DESC
LIMIT 5;DESC是倒序
4.where
用在order by之前
SELECT name,film_year FROM movies
WHERE name = '哈利波特'
ORDER BY film_year;5.派生列
假如表movies里没有列count、country
SELECT film_year,ticket_price,film_year/ticket_price AS count'England'AS country
FROM movies
WHERE name = '哈利波特'
ORDER BY film_year
LIMIT 5;逻辑运算符
1.like.
SELECT name FROM movies
WHERE name LIKE '%哈利%';2.in.
SELECT name,director FROM movies
WHERE name IN ('哈利波特','魔戒');3.not.
SELECT name FROM movies
WHERE name NOT LIKE '哈利%';SELECT name,director FROM movies
WHERE name NOT IN ('哈利波特','魔戒');4.and 与 between
SELECT name, director FROM movies
WHERE film_year = 2000 and name = '哈利波特';SELECT name,director FROM movies
WHERE film_day NOT BETWEEN 2000-01-01 AND 2010-01-01;between包含端点值，但对于时间2010-01-01是2010-01-01 0:00:00
5.or.
SELECT name,director FROM movies
WHERE (film_year = 2000 OR film_year = 2010) AND name = '哈利波特'
ORDER BY film_year;
