实训任务二

解释和分析如下带参数SQL语句的作用

1.string sqlTest = "select count(*) from users where usersname=@usersnaem and userspwd=@userspwd";      统计用户名为‘rr’,密码为‘rr’的总人数

 

2.string sqlTest = @"select id from users where usersname=@usersname and userspwd=@userspwd";     

 查询用户名为‘zy’，密码为‘zy’的用户id是多少

3.string sqlTest = "select * from Users";

查询用户表里面的全部信息

4.string sql = "insert into users values(@a,@b,@c)";

为用户表添加一行记录，用户名为‘1’，密码为‘2’，用户昵称为‘3’的用户

5.string sql = @"update users set usersname=@a ,userspwd=@b, UserCompellation=@c where id=@d";

修改id为‘1’的用户的用户名为‘lz’，密码为‘lz’，昵称为‘haha’

 

6.string sql = @"delete users where id=@a"

删除id为‘36’的用户

 

7.string sql = "select id,usersname from users";

查询用户表里面id列和用户名列的信息

 

 9.string  sqlTest = "select top(1) cbid,cbstartdate from ConsumerBill where  tableid=@tableid order by CBStartDate desc ";

查询消费票据表中餐桌编号为‘2’的编号和开单时间 然后按照降序排列并显示首条记录