String sqlCount="select count(*) from usertable where username='"+ userName+"'";这句话 什么意思啊! 这句话输出出来就是 select count(*) from usertable where username='你的变量 ......
SELECT * from alarms where id in (select resource_id from res_products where product=22) 这个语句在mysql中为什么不能执行?我的mysql数据库是5.0.27版本的! 如果实在不行那么该用个什么语句代替效率更高呢 ......
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was51093 seconds ago.The last packet sent successfully to the server was 5 ......