java - 如何根据表中的客户数将sql查询中的计数值存储到变量中以创建customerid？

Question

我想将收到的计数值存储到变量计数中，然后可以将其附加到字符串以准备客户 ID，但它给了我光标无效错误。请看下面并帮助我。提前致谢。:)

    **package components;
    import java.awt.geom.GeneralPath;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    public class genrateid {

        public void generateid(){

    int count;


            try {
                Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                Connection conn = DriverManager.getConnection("jdbc:odbc:XE",
                        "system", "tiger");
                System.out.println("Connection Successfull");
                System.out.println(conn); 

                //--------------------------------------------------------------------
                Statement stmt = conn.createStatement();
                String query1= "select count(*) as customercount from customers";

                ResultSet rs= stmt.executeQuery(query1);
    count = rs.getInt(1);
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }


            }

        public static void main(String[] args) {
            genrateid gen = new genrateid();
            gen.generateid();

        }
        }**


I am receiving the following error in  in eclipse IDE:

输出：

Connection Successfull
sun.jdbc.odbc.JdbcOdbcConnection@39b27b
java.sql.SQLException: [Microsoft][ODBC Driver Manager] Invalid cursor state
    at sun.jdbc.odbc.JdbcOdbc.createSQLException(Unknown Source)
    at sun.jdbc.odbc.JdbcOdbc.standardError(Unknown Source)
    at sun.jdbc.odbc.JdbcOdbc.SQLGetDataInteger(Unknown Source)
    at sun.jdbc.odbc.JdbcOdbcResultSet.getDataInteger(Unknown Source)
    at sun.jdbc.odbc.JdbcOdbcResultSet.getInt(Unknown Source)
    at components.genrateid.generateid(genrateid.java:29)
    at components.genrateid.main(genrateid.java:43)

Answer 1

插入这一行

if(rs.next()) 

前

  count = rs.getInt(1); 

你会好起来的。但是，正如 Dems 所说，考虑使用 IDENTITY 列（或者因为您使用的是 Oracle - SEQUENCE）