我在选民登记册上有一个甲骨文数据库。为了检查一个投票者是否曾经投票过，我创建了一个函数PreviouslyVoted(election_code, electorate_code, voter_id)，如下所示。

create or replace FUNCTION previouslyVoted(election_code_in IN NUMBER, electorate_id_in IN NUMBER, voter_id_in IN NUMBER)
RETURN BOOLEAN IS
voter_id_temp NUMBER;
BEGIN
    SELECT COUNT(*) INTO voter_id_temp
    FROM ballot_issuance bi
    WHERE bi.electorate_id = electorate_id_in
    AND bi.election_serial_number = election_code_in
    AND bi.voter_id = voter_id_in;

RETURN voter_id_temp > 0 ;
END;

现在我想从PHP服务器调用它。
我尝试运行发送以下查询：

Select previouslyVoted(" .ELECTION ."," .ELECTORATE .", $oracle_voter_id) "Result" FROM dual;

但没有成功。下面的错误是ERROR：

ORA-00902: invalid datatype
00902. 00000 -  "invalid datatype"
*Cause:    
*Action:
Error at Line: 1 Column: 8

我试着去sqldeveloper和运行

Select previouslyVoted(20190404,1,13321) "Result" FROM dual;

又犯了同样的错误。我试着把表达式扩展到

SELECT
    "S4026115"."PREVIOUSLYVOTED"(20190404, 1, 13321) "Result"
FROM
    "SYS"."DUAL" "A1";

但再次得到同样的错误。有趣的是：如果我把它 Package 在一个像下面这样的过程，它完全正常工作.

create or replace PROCEDURE runprevvoted
AS
   has_voted BOOLEAN;
BEGIN
   has_voted := previouslyVoted(20190404, 1, 13321);
   IF has_voted THEN
      DBMS_OUTPUT.PUT_LINE('This voter has previously voted.');
   ELSE
      DBMS_OUTPUT.PUT_LINE('This voter has not previously voted.');
   END IF;
END;

希望有人能帮助我了解我做错了什么！提前感谢您