如何将主键的 ID 填充到外键

Question

我刚开始学习 Java JDBC，我尝试创建一个示例项目。我创建了两个 Prepared Statements，我在其中为我的表插入两个查询。主键的第一个表和外键的第二个表。使用 Statement_RETURN.GENERATED_KEYS 正在返回主键的 Id，但在我的外键中它没有填充并给我一个 null 值。

父表

子表

查询：

    String insertALLSECTION_LIST = "INSERT INTO ALLSECTIONS_LIST (SECTION_NAME)"
            + "VALUES (?)";
    String insertALLSECTIONS_SETTINGS = "INSERT INTO ALLSECTIONS_SETTINGS (SECTION_POPULIMIT,ROOM_ASSGN,ADVISER_ASSIGNED,SESSION_ASSIGNED,YRLEVEL_ASSGN,SCHOOL_YEAR)"
            + "VALUES(?,?,?,?,?,?)";

准备好的陈述

    ResultSet generatedKeys = null;
    try (Connection myConn = DBUtil.connect())//Connection
    {
            myConn.setAutoCommit(false);//Turn off auto commit
            try (PreparedStatement myPs = myConn.prepareStatement(insertALLSECTION_LIST,Statement.RETURN_GENERATED_KEYS))//Prepared Statement
            {
                myPs.setString(1,inputSectionName);

                myPs.executeUpdate();

                myConn.commit();

                generatedKeys = myPs.getGeneratedKeys();
                if (generatedKeys.next())//Return ID
                {
                    sectionID = generatedKeys.getInt(1);
                }
                else
                {
                    throw new SQLException("No generated section ID returned");
                }

            }//end of try
            finally 
            {
                if (generatedKeys != null) generatedKeys.close();
            }//end of finally
            try (PreparedStatement myPs = myConn.prepareStatement(insertALLSECTIONS_SETTINGS))//Prepared Statement
            {
                myPs.setInt(1,inputStudentLimit);
                myPs.setString(2, inputRoomAssign);
                myPs.setString(3, inputAdviserAssign);
                myPs.setString(4, inputSession);
                myPs.setString(5, inputYearLevel);
                myPs.setString(6, inputSchoolYear);

                myPs.executeUpdate();

                myConn.commit();

                JOptionPane.showMessageDialog(null, "Insert Successful");
            }//end of try
    }//end of try       

第一个表（ALLSECTIONS_LIST）

正如您在此处看到的，主键正在填充。

第二张表（ALLSECTIONS_SETTINGS）

在这里我的 SECTION_ID 列给了我空值。

但是当我为我的表运行查询时。仍然给我的外键一个 Null 值。随意发表评论。谢谢。

Answer 1

当您通过第一个 Prepared Statement 取回自动生成的密钥后，您必须手动将其插入到另一个表中。

以下是修改后的查询：

String insertALLSECTION_LIST = "INSERT INTO ALLSECTIONS_LIST (SECTION_NAME)"
        + "VALUES (?)";

String insertALLSECTIONS_SETTINGS = "INSERT INTO ALLSECTIONS_SETTINGS (SECTION_ID,
        SECTION_POPULIMIT,ROOM_ASSGN,ADVISER_ASSIGNED,
        SESSION_ASSIGNED,YRLEVEL_ASSGN,SCHOOL_YEAR)"
        + "VALUES(?,?,?,?,?,?,?)";

这里是sn-p的代码：

ResultSet generatedKeys = null;
try (Connection myConn = DBUtil.connect()) {
    myConn.setAutoCommit(false);
    try (PreparedStatement myPs = myConn.prepareStatement(insertALLSECTION_LIST,
      Statement.RETURN_GENERATED_KEYS)) {
        myPs.setString(1,inputSectionName);
        myPs.executeUpdate();

        myConn.commit();
        generatedKeys = myPs.getGeneratedKeys();
        if (generatedKeys.next()) {
            sectionID = generatedKeys.getInt(1);
        } else {
            throw new SQLException("No generated section ID returned");
        }
    } finally {
        if (generatedKeys != null) generatedKeys.close();
    }

    try (PreparedStatement myPs = myConn.prepareStatement(insertALLSECTIONS_SETTINGS)) {
        /* Note : Change Here */
        myPs.setInt(1, sectionID);
        myPs.setInt(2, inputStudentLimit);
        myPs.setString(3, inputRoomAssign);
        myPs.setString(4, inputAdviserAssign);
        myPs.setString(5, inputSession);
        myPs.setString(6, inputYearLevel);
        myPs.setString(7, inputSchoolYear);
        myPs.executeUpdate();

        myConn.commit();
        JOptionPane.showMessageDialog(null, "Insert Successful");
    }
}