ORA-00904错误信息

问题现象：在某表中使用查询语句，结果报某个字段不能识别错误ORA-00904: "callid": invalid identifier，但是使用desc显示时却存在该字段，然后将查询语句更换成加双引号，执行即可。

错误官方解释：

ORA-00904: string: invalid identifier Cause: The column name entered is either missing or invalid. Action: Enter a valid column name. A valid column name must begin with a letter, be less than or equal to 30 characters, and consist of only alphanumeric characters and the special characters $, _, and #. If it contains other characters, then it must be enclosed in double quotation marks. It may not be a reserved word.  

实际原因：数据库中设置了大小写区别的设置。