mysql之SQL入门与提升（一）

一.基本的增删改查

1.1首先建一张表

DROP TABLE IF EXISTS `websites`;
CREATE TABLE `websites` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` char(20) NOT NULL DEFAULT '' COMMENT '站点名称',
`url` varchar(255) NOT NULL DEFAULT '',
`alexa` int(11) NOT NULL DEFAULT '0' COMMENT 'Alexa 排名',
`country` char(10) NOT NULL DEFAULT '' COMMENT '国家',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of `websites`
-- ----------------------------
BEGIN;
INSERT INTO `websites` VALUES ('1', 'Google', 'https://www.google.cm/', '1', 'USA'), ('2', '淘宝', 'https://www.taobao.com/', '13', 'CN'), ('3', '京东', 'http://www.runoob.com/', '4689', 'CN'), ('4', '微博', 'http://weibo.com/', '20', 'CN'), ('5', 'Facebook', 'https://www.facebook.com/', '3', 'USA');
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;

1.2SQL INSERT INTO 语句

第一种形式无需指定要插入数据的列名，只需提供被插入的值即可：

INSERT INTO table_name
VALUES (value1,value2,value3,...);

第二种形式需要指定列名及被插入的值：

INSERT INTO table_name (column1,column2,column3,...)
VALUES (value1,value2,value3,...);

实例

INSERT INTO Websites (name, url, alexa, country) VALUES ('百度','https://www.baidu.com/','4','CN');

1.3SQL DELETE 语句

SQL DELETE 语法

DELETE FROM table_name
WHERE some_column=some_value;

实例

DELETE FROM Websites WHERE name='百度' AND country='CN';

1.4SQL UPDATE 语句

SQL UPDATE 语法

UPDATE table_name
SET column1=value1,column2=value2,...
WHERE some_column=some_value;

实例

UPDATE Websites SET alexa='5000', country='USA' WHERE name='京东';

1.5SQL SELECT 语句

SQL SELECT 语法

SELECT column_name,column_name
FROM table_name;

与

SELECT * FROM table_name;

实例

SELECT name,country FROM Websites;

SELECT * FROM Websites;

1.6SQL SELECT DISTINCT 语句

SQL SELECT DISTINCT 语法

SELECT DISTINCT column_name,column_name
FROM table_name;

实例

SELECT DISTINCT country FROM Websites;

1.7SQL WHERE 子句

SQL WHERE 语法

SELECT column_name,column_name
FROM table_name
WHERE column_name operator value;

实例

SELECT * FROM Websites WHERE country='CN';

1.8SQL AND & OR 运算符

如果第一个条件和第二个条件都成立，则 AND 运算符显示一条记录。

如果第一个条件和第二个条件中只要有一个成立，则 OR 运算符显示一条记录。

实例

SELECT * FROM Websites WHERE country='CN' AND alexa > 50;

1.9SQL ORDER BY 关键字

ORDER BY 关键字用于对结果集按照一个列或者多个列进行排序。

ORDER BY 关键字默认按照升序对记录进行排序。如果需要按照降序对记录进行排序，您可以使用 DESC 关键字。

SQL ORDER BY 语法

SELECT column_name,column_name
FROM table_name
ORDER BY column_name,column_name ASC|DESC;

实例

SELECT * FROM Websites ORDER BY alexa;

SELECT * FROM Websites ORDER BY alexa DESC;

SELECT * FROM Websites ORDER BY country,alexa;

ORDER BY 多列的时候，eg:

order by A,B        这个时候都是默认按升序排列
order by A desc,B   这个时候 A 降序，B 升序排列
order by A ,B desc  这个时候 A 升序，B 降序排列

二.SQL进阶篇
2.1LIMIT 限制数量，对于拥有数千条记录的大型表来说，是非常有用的。
SELECT *
FROM Websites
LIMIT 5;
2.2SQL LIKE

SQL LIKE 语法

SELECT column_name(s)
FROM table_name
WHERE column_name LIKE pattern;

实例

SELECT * FROM Websites WHERE name LIKE 'G%';
SELECT * FROM Websites WHERE name LIKE '%oo%';

SELECT * FROM Websites WHERE name NOT LIKE '%oo%';

2.3SQL 通配符

2.3.1 % 通配符

实例

SELECT * FROM Websites WHERE url LIKE 'https%'

SELECT * FROM Websites WHERE url LIKE '%oo%';

2.3.2 _ 通配符

实例

SELECT * FROM Websites WHERE name LIKE '_oogle';

SELECT * FROM Websites WHERE name LIKE 'G_o_le';

2.3.3 REGEXP 或 NOT REGEXP通配符

SQL 语句选取 name 以 "G"、"F" 或 "s" 开始的所有网站：

实例

SELECT * FROM Websites WHERE name REGEXP '^[GFs]';
SELECT * FROM Websites WHERE name REGEXP '^[A-H]';

下面的 SQL 语句选取 name 不以 A 到 H 字母开头的网站：

SELECT * FROM Websites WHERE name REGEXP '^[^A-H]';

2.4SQL IN

SQL IN 语法

SELECT column_name(s)
FROM table_name
WHERE column_name IN (value1,value2,...);

实例

SELECT * FROM Websites WHERE name IN ('Google','菜鸟教程');

IN 与 = 的异同
- 相同点：均在WHERE中使用作为筛选条件之一、均是等于的含义
- 不同点：IN可以规定多个值，等于规定一个值
IN
```
SELECT column_name(s)
FROM table_name
WHERE column_name IN (value1,value2,...);
```
=
```
SELECT column_name(s)
FROM table_name
WHERE column_name=value1;
```
in 与 = 的转换
```
select * from Websites where name in ('Google','百度');
```
可以转换成 = 的表达：

select * from Websites where name='Google' or name='百度';
```
2.5SQL BETWEEN 
```
SQL BETWEEN 语法
SELECT column_name(s)
FROM table_name
WHERE column_name BETWEEN value1 AND value2;

实例

SELECT * FROM Websites WHERE alexa BETWEEN 1 AND 20;
SELECT * FROM Websites WHERE alexa NOT BETWEEN 1 AND 20;

下面的 SQL 语句选取 alexa 介于 1 和 20 之间但 country 不为 USA 和 IND 的所有网站：

SELECT * FROM Websites WHERE (alexa BETWEEN 1 AND 20)AND country NOT IN ('USA', 'IND');
下面的 SQL 语句选取 name 以介于 'A' 和 'H' 之间字母开始的所有网站：

SELECT * FROM Websites WHERE name BETWEEN 'A' AND 'H';

下面的 SQL 语句选取 name 不介于 'A' 和 'H' 之间字母开始的所有网站

SELECT * FROM Websites WHERE name NOT BETWEEN 'A' AND 'H';

SELECT * FROM access_log WHERE date BETWEEN '2016-05-10' AND '2016-05-14';
```
 
```