在用union联合查询排序时遇到了以下异常：
org.springframework.jdbc.BadSqlGrammarException: PreparedStatementCallback; bad SQL grammar [select a.table_name as tableName,a.flow_name as flowName, a.action_name as actionName,a.field_name as fieldName,a.field_title as fieldTitle, a.field_right as fieldRight,a.action_right_guid as guid,a.table_title as tableTitle from fwt_action_right a where a.table_name=? and flow_name=? and action_name=? union select b.table_name as tableName,'' as flowName,'' as actionName, b.field_name as fieldName,b.field_title as fieldTitle,'' as fieldRight,'' as guid,'' as tableTitle from adam_field_info b where b.table_name=? and b.field_name not in (select field_name from fwt_action_right a where table_name=? and flow_name=? and action_name=? ) order by a.fieldName asc ]; nested exception is java.sql.SQLException: ORA-00904: "A"."FIELDNAME": 标识符无效org.springframework
