這個是什么原因呢?有哪位能幫忙解決一下嗎

org.springframework.jdbc.UncategorizedSQLException:
### Error querying database.? Cause: java.sql.SQLException: No database selected
### The error may exist in file [D:\eclipse_javaweb\seckill\target\classes\mapper\SeckillDao.xml]
### The error may involve org.Seckill.dao.SeckillDao.queryById-Inline
### The error occurred while setting parameters
### SQL: select seckill_id,name,number,create_time,start_time,end_time from seckill where seckill_id = ?
### Cause: java.sql.SQLException: No database selected
; uncategorized SQLException for SQL []; SQL state [3D000]; error code [1046]; No database selected; nested exception is java.sql.SQLException: No database selected