ORA-25471: attribute name not specified for variable: string
Cause: An attempt to evaluate was made, which failed because one of the attribute values for the specified variable had a NULL attribute name.
Action: Check the list of attribute values, and try again with a valid attribute name.
ORA-25471：当程序调用 DBMS_SESSION.SET_IDENTIFIER() 函数，但没有指定变量名称时，会出现ORA-25471 错误。
Cause: DBMS_SESSION.SET_IDENTIFIER call was made without the 2nd argument (the attribute name).
Action: Make sure the 2nd argument is specified to the DBMS_SESSION.SET_IDENTIFIER call.
比如代码如下：
DECLARE
v_val1 VARCHAR2(100);
BEGIN
v_val1 := ‘value1’;
DBMS_SESSION.SET_IDENTIFIER(v_val1);
END;
调用了DBMS_SESSION.SET_IDENTIFIER()函数，但没有给它设置变量名，会导致ORA-25471错误。
1. 修改程序代码，设置正确变量名。
例如修改上述代码为：
DECLARE
v_val1 VARCHAR2(100);
BEGIN
v_val1 := ‘value1’;
DBMS_SESSION.SET_IDENTIFIER(v_val1, ‘val1’);
END;
2. 重新编译程序，重新执行。