• 第10章 使用MySQL数据库


    1.在数据库中插入数据:INSERT语句;

            如://插入一整行:

                   insert into customers values

                         (NULL,’…’,’…’,’…’), … ;

                   //插入一行中指定的列内容:

                   insert into customers (name,city) values

                        (‘…’,’…’);

                   //等同于以下形式

                  insert into cutomers

                  set name=’…’,

                        city=’…’;

    2.通过输入cmd命令运行sql脚本:

               >mysql –u root –p books < G:/Apache/htdocs/ch10/book_insert.sql

               或(已进入mysql的情况下)mysql> source G:/Apache/htdocs/ch10/book_insert.sql;

    3.1.从数据库中获取数据:

               //获取表中的指定列 

              select name,city

              from customers;

              //获得表中所有的列和行

             select *

             from order_items;

             //获得表中所有列中符合特定条件的行

             select *

             from orders

             where customerid=3 ;

             //可以用简单的操作符、模式匹配语法及AND和OR

             select *

             from orders

             where customerid=3 or customerid=4 ;

    3.2.从多个表中获取数据:

         ①简单双表关联:

                  select orders.orderid, orders.amount, orders.date

                  from customers, orders

                  where customers.name=’…’

                  and customers.customerid=orders.customerid;

        ②查找不匹配行:

               【左关联:在两个表之间指定的关联条件下匹配数据行,如果右边的表中没有匹配行,结果中就会增加一行,该行右边的列内容为NULL】(对应的右关联同理)

                //ON语法

                select customers.customerid, customers.name, orders.orderid

               from customers left join orders

               on customers.customerid=orders.customerid;

               //USING语法,不需要指定连接属性所来自的表

               select customers.customerid, customers.name

               from customers left join orders

               using (customerid)

              where orders.orderid is null;

       ③使用表的别名:Aliases (在一个查询的开始创建表的别名,然后在整个查询过程中使用)

              select c.name

              from customers as c, orders as o, order_items as oi, books as b

              where c.customerid=o.customerid

              and o.orderid=oi.orderid

              and oi.isbn=b.isbn

              and b.title like ‘%Java%’;

    3.3.以特定顺序获取数据:

            如://按照名升序排列

                   select name, address

                   from customers

                   order by name asc;    //ORDER BY子句默认为升序(即asc),desc为降序

    4.分组、合计数据:

             合计函数:avg(列),count(项目),min(列),max(列),std(列),stddev(列),sun(列)

    5.LIMIT:

             select name

             from customers

             limit 2, 3;     //从customers表中选择name列,返回3行,从第2行开始

    6.更新数据库记录:UPDATE语句

                   如: update  customers

                           set …

                          where …

                          order by …

                          limit …

    7.修改表:ALTER TABLE语句

             如://改变名称允许的最大长度

                    alter table customers

                    modify name char(70) not null;

                    //删除一列

                    alter table orders

                    drop tax;

    8.删除数据库中的记录:

           ①DELETE语句:

                      如:  delete from customers

                               where customerid=5;

           ②删除表:    如:drop table tablename;

           ③删除整个数据库:   如:drop database dbname;

    9.cmd退出mysql:

           mysql> /q

      或 mysql> exit   或 mysql> quit

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  • 原文地址:https://www.cnblogs.com/atmacmer/p/5865640.html
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