如何將一個表中的主鍵值插入另一個表中的外鍵列中？

Question

我是新來的SQL和一般編程，所以如果答案是明顯的，請耐心等待。我有一張名爲「門票」的表，其中包含主鍵ticket_id。我還有另一個名爲「contact_info」的表，它存儲了創建票的人的聯繫信息。在這個表中，ticket_id是一個叫做ticket_number的外鍵。用戶通過GUI插入票證，並且ticket_number在數據庫中自動遞增。如何選擇ticket_number並將其插入到包含創建該票證的人的contact_info的行中？

這是代碼，現在，它不會做什麼我就想到：

try{ 
       //Open a connection 
       System.out.println("Connecting to a selected database..."); 
       this.connection = DriverManager.getConnection(url, username, password); 
       System.out.println("Connected database successfully..."); 

       //Execute a query 
       System.out.println("Inserting records into the table..."); 
       PreparedStatement pstmt = connection.prepareStatement(" INSERT INTO s_fuse_ticket_table " 
           + " (summary, status, severity, classification, type, internal_notes, description, assignees) " 
           + " VALUES (?, ?, ?, ?, ?, ?, ?, ?)"); 

          if(summary.getText().equals("")){ 
           throw new SQLException("Summary cannot be blank"); 
          } 
          pstmt.setString(1, summary.getText()); 
        pstmt.setString(2, status.getSelectionModel().getSelectedItem().toString()); 
        pstmt.setString(3, severity.getSelectionModel().getSelectedItem().toString()); 
          if(classification.getSelectionModel().getSelectedItem().toString().equals("Make a Selection")){ 
           throw new SQLException("Please select a classification"); 
          } 
          pstmt.setString(4, classification.getSelectionModel().getSelectedItem().toString()); 
          if(type.getSelectionModel().getSelectedItem().toString().equals("Make a Selection")){ 
           throw new SQLException("Please select a type"); 
          } 
          pstmt.setString(5, type.getSelectionModel().getSelectedItem().toString()); 
          pstmt.setString(6, internalNotes.getText()); 
          pstmt.setString(7, description.getText()); 
          pstmt.setString(8, assignee.getSelectionModel().getSelectedItem().toString()); 
        pstmt.executeUpdate(); 

          //Execute a query 
         System.out.println("Inserting records into the table..."); 
         PreparedStatement pstmt2 = connection.prepareStatement(" INSERT INTO s_fuse_contact_info_table " 
           + " (ticket_number, email, last_name, first_name) " 
           + " VALUES (?, ?, ?, ?)"); 

          pstmt2.setString(1, ("SELECT ticket_id FROM s_fuse_ticket_table")); 
          /*if(!email.getText().contains("@") && !email.getText().contains(".")){ 

          }*/ 
          pstmt2.setString(2, email.getText()); 
          pstmt2.setString(3, lname.getText()); 
          pstmt2.setString(4, fname.getText()); 
        pstmt2.executeUpdate(); 
      }catch(SQLException se){ 
       //Handle errors for JDBC 
       se.printStackTrace(); 
      }catch(Exception e){ 
       //Handle errors for Class.forName 
       e.printStackTrace(); 
      }finally{ 
       //finally block used to close resources 
       try{ 
       if(stmt!=null) 
       { 
        connection.close(); 
       } 
       }catch(SQLException se){ 
       }// do nothing 
       try{ 
       if(connection!=null) 
       { 
        connection.close(); 
       } 
       }catch(SQLException se){ 
       se.printStackTrace(); 
       }//end finally try 
      }//end try 
      System.out.println("Goodbye!"); 

Answer 1

不同DBMS」有不同的方法來做到這一點 - 是指this question一個相當全面的清單。

另一種方式是使用交易。當MVCC DBMS處於合適的隔離級別（可重複讀取或可序列化）時，當您啓動一個新的連接時，您將擁有您自己的db視圖，因此您可以在主表中輸入INSERT INTO，然後在SELECT的最後一行匹配您的插入和確信它屬於你。無論如何，將這種插入方式捆綁在一起是一個不錯的主意，因爲它可以防止任何不一致的數據進入系統 - 只要確保事後提交即可！