2017/12/4周一
一天看了一半的图灵程序设计丛书的这本《SQL必知必会》第4版，数据库入门经典书
平台：Windows下的命令行操作
数据库：MYSQL
1.安装会出现的问题
【解决方案】MySQL-5.7.9 服务无法启动-“NET HELPMSG 3534”
http://blog.csdn.net/i_am_wangbo/article/details/49999407
解决方法：删除data文件夹，重新初始化
2.参考的是易百教程网站的MySQLhttp://www.yiibai.com/mysql/
下面是书的前一半记录的笔记：
show databases;
use mysql1;show tables;
select * from products;
####注释方法1：任意位置
--注释方法2：得出现在命令行 行后
/*注释方法3：任意位置*/
##第二章 检索数据
--显示全部 ‘*’
select * from products;
--显示3列，逗号‘，’隔开
select prod_name, vend_id, prod_price from products;
--显示1列
select prod_name from products;
--只显示5行 ‘limit 5’
select prod_name from products LIMIT 5;
--显示2行后的3行，即第3行到第5行 ‘limit 3 offset 2’或 ‘LIMIT 2,3’
select prod_name from products LIMIT 3 OFFSET 2;
select prod_name from products LIMIT 2,3;
--显示不重复的不同的值 ‘DISTINCT’
select DISTINCT vend_id from products;
##第三章 排序检索数据 “ORDER by prod_price DESC”
--按照‘vend_id’排序 “ORDER by prod_price DESC”（默认升序ASC（ascending）
--ASC a scending 递增
--DESC de scending 递减
select prod_name, vend_id, prod_price from products ORDER by prod_price;
select prod_name, vend_id, prod_price from products ORDER by prod_price, prod_name;
select prod_name, vend_id, prod_price from products ORDER by prod_price DESC, prod_name;
##第四章 过滤数据 "WHERE prod_price = 3.49" BETWEEN 5 and 10
select prod_id, prod_name, prod_price from products WHERE prod_price = 3.49;
select prod_id, prod_name, prod_price from products WHERE prod_price < 10;
select prod_id, prod_name, prod_price from products WHERE prod_price BETWEEN 5 and 10;
--ORDER应该在WHERE之后
select prod_id, prod_name, prod_price from products WHERE prod_price < 10 ORDER by prod_price DESC;
--IS NULL判断是否为NULL值
select * from customers where cust_email IS NULL;
--AND ，字符串只用单引号‘’表示
select prod_id, vend_id, prod_name, prod_price from products
WHERE prod_price < 10 AND vend_id = 'DLL01';
--OR
select prod_id, vend_id, prod_name, prod_price from products
WHERE prod_price < 5 or vend_id = 'FNG01';
--AND OR混用/ AND优先级更高，使用时最好加括号 / 注意以下2句的区别
select prod_id, vend_id, prod_name, prod_price from products
WHERE vend_id = 'DLL01' OR vend_id = 'BRS01' AND prod_price >=10;
select prod_id, vend_id, prod_name, prod_price from products
(WHERE vend_id = 'DLL01' OR vend_id = 'BRS01') AND prod_price >=10;
#第五章 高级过滤 IN NOT
--IN vend_id IN ( 'DLL01','BRS01' ) 与or类似，但执行更快，语法更清晰
select prod_id, vend_id, prod_name, prod_price from products
WHERE vend_id IN ( 'DLL01','BRS01' ) ORDER BY prod_name;
--NOT NOT vend_id = 'DLL01' 找出与条件不匹配的行
select prod_id, vend_id, prod_name, prod_price from products
WHERE NOT vend_id = 'DLL01' ORDER BY prod_name;
#第六章 通配符LIKE '% _ '
#注意通配符要用LIKE 不能用 = ，因为不相等
--LIKE '%'
select prod_id, vend_id, prod_name, prod_price from products
WHERE vend_id LIKE 'D%' ORDER BY prod_name;
--'_'下划线 只能匹配单个字符
select prod_id, vend_id, prod_name, prod_price from products
WHERE vend_id LIKE 'D_L01' ORDER BY prod_name;
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--CONCAT 拼接连接多个数组 ,字符串用单引号包括
select CONCAT(vend_name, ' ','(',vend_country,')') from vendors;
--AS 为新列命名
select CONCAT(vend_name, ' ','(',vend_country,')') AS result from vendors;
--计算新的一列，命名为result
select prod_id,quantity,item_price, quantity*item_price AS result from orderitems;
--RTRIM() LTRIM() TRIM()去除字符串的空格
#总结：select为测试、检验、计算提供了很好的方法
#第8章 函数
--UPPER()转换为大写字符串 LOWER()
select vend_name, UPPER(vend_name) as result from vendors;
--YEAR()
select order_num from orders where year(order_date) = 2012;
#总结，函数各数据库软件不一致，移植性不好
#第9章 汇总数据
--聚集函数，各软件都挺一致
AVG() COUNG() MAX() MIN() SUM()
#第10章