java mysql 使用心得

不要使用mysql的关键字,如key.       2014.4.13

1.获取最大值 String device_sql= "select max(id) id  from user";

2.创建一条数据

String create_sql="insert into unit (user_id,device_id,index_in_device) values ("+device_user_id+","+device_id+","+unit_id+")";
db1.statement.execute(create_sql);

=== insert into unit (user_id,device_id,index_in_device) values (1,1,11)

不要使用 rs=db1.statement.execute(create_sql);  否则出错.

不能使用 db1.statement.executeQuery(sql);

2.更新数据

 String sql= "update unit set "+field_id+" ='"+value+"' where device_id="+device_id+" and index_in_device="+unit_id+"";
 
     int rs;
   
    rs = db1.statement.executeUpdate(sql);

 3.插入数据

String create_sql="insert into device (user_id,name,app_key,index_id) values ("+user_id+",'"+device_name+"','"+device_key+"',"+(device_max_index+1)+")";
       db1.statement.execute(create_sql);

4.获取刚插入数据的自动序列值

 String create_sql="insert into device (user_id,name,app_key,index_id) values ("+user_id+",'"+device_name+"','"+device_key+"',"+(device_max_index+1)+")";
       db1.statement.execute(create_sql);
       rs=db1.statement.executeQuery("select  last_insert_id()");
       if(rs.next())
       {
        newDeviceId=rs.getInt(1);
       }