如何使用netbeans使用数据库语句进行计数

Question

我在计算输入并将其与数据库中的数据字段进行匹配，然后计算状态并显示输入已借入的书籍数量。

 Statement statement = conn.createStatement(); 

     String sql = "SELECT COUNT(jtfMemberID.getText()) as num FROM LOAN WHERE LOAN_STATUS='BORROWED'"; 

     ResultSet rs1 = statement.executeQuery(sql); 
     int personCount = 0; 

     if(rs1.next()) { 
      personCount = rs1.getInt("num"); 
      jlbBookBorrow.setText(rs1.getString(personCount)); 
     }else{ 
      jlbBookBorrow.setText("0"); 
     } 

Answer 1

文本jtfMemberID.getText()将字面上你SQLString解释。你需要提取出来：

String sql = "SELECT COUNT(" + jtfMemberID.getText() + ") as num FROM LOAN WHERE LOAN_STATUS='BORROWED'"; 

此外，为了防止SQL Injection攻击，可以考虑使用PreparedStatement。