修复无效标识符的错误

Question

我正在创建一个包，然后在其中创建一个存储过程。包装及流程如下：

create or replace package test_system is
    type ref_cursor is ref cursor;
procedure demo_show_students(p_gpa IN STUDENTS.gpa%TYPE,p_ref_cursor  OUT ref_cursor );
end test_system;
/

create or replace package body test_system is
procedure demo_show_students(p_gpa IN STUDENTS.gpa%TYPE,p_ref_cursor   OUT ref_cursor )
is
v_sql_str varchar2(4000);
begin
v_sql_str:='select sid,firstname,lastname,status,gpa,email from students where gpa = p_gpa';
open p_ref_cursor for v_sql_str;
end demo_show_students;
end test_system;

以下是 java 代码，即用于链接两者的 pl/SQL 代码，但它给了我一个问题：

import java.sql.*;

import oracle.jdbc.OracleTypes;

public class ShowStudents {

public void showStudents() {

    try {

        // Connection to Oracle server
        OracleDataSource ds = new oracle.jdbc.pool.OracleDataSource();
        ds.setURL("jdbc:oracle:thin:@localhost:1521:xe");
        Connection conn = ds.getConnection("*****", "*****");

        String val = '4'+"";
        CallableStatement cs = conn.prepareCall("{call        
        test_system.demo_show_students(?,?)}");
        cs.setString(1, val);

        cs.registerOutParameter(2, OracleTypes.CURSOR);
        cs.execute();
        ResultSet rs = (ResultSet)cs.getObject(2);

        while (rs.next()) {
            System.out.println(rs.getString(1) + "\t" +
                rs.getString(2) + "\t" + rs.getString(3) + 
                rs.getString(4) + 
                "\t" + rs.getDouble(5) + "\t" +
                rs.getString(6));
        }


        cs.close();

    } catch (SQLException ex) {
        System.out.println("\n*** SQLException caught ***\n");
        ex.printStackTrace();
    } catch (Exception e) {
        System.out.println("\n*** other Exception caught ***\n");
    }
}
}



Exception : 

*** SQLException caught ***
ORA-00904: "P_GPA": invalid identifier
ORA-06512: at "PROJECT2.TEST_SYSTEM", line 7
ORA-06512: at line 1

谁能告诉我如何解决这个错误。

Answer 1

oracle 无法识别变量p_gpa。您可以通过两种方式做到这一点：

1) 放置一个占位符

  v_sql_str:='select sid,firstname,lastname,status,gpa,email from students where gpa = :p_gpa';

  open p_ref_cursor for v_sql_str using p_gpa;

2) 直接将查询写成：

open p_ref_cursor for   
select sid,firstname,lastname,status,gpa,email 
from students where gpa = p_gpa;