java - 如何在jsp中选择数据库的最后一行？

Question

我无法在 jsp 中显示数据库的最后一行。我已经尝试打印 rs.getString(1)，但它不起作用。

ResultSet rs = st.executeQuery("Select MAX(CustomerID) from Customer");  
while(rs.next()){out.print(rs.getString(1));}

Answer 1

我不知道这是不是你想要的，但如果你想获得整行，有一些方法可以实现这一点

ResultSet rs = st.executeQuery("select max(customerid) as id from customer");
rs.next();
String id = rs.getString("id");
rs = st.executeQuery("select field_a, field_b from customer where customerid = " + id);
rs.next();
String row = id + "," + rs.getString("field_a") + "," + rs.getString("field_b");
out.println(row);

当然，您需要将 field_a 和 field_b 列替换为您的 customer 表中的列，并根据您的需要添加或删除列需要。

较短的方法是使用 order by 和 limit 关键字，如下所示

ResultSet rs = st.executeQuery("select customerid, field_a, field_b from customer order by customerid desc limit 1");
rs.next();
String row = rs.getString("customerid") + "," + rs.getString("field_a") + "," + rs.getString("field_b");
out.println(row);

确保将 primary key 或 unique 约束添加到 customerid 列以提高这两种方法的性能。