没有嵌套，结果集无效

String sql1 = "select jname from (select * from j order by dbms_random.value()) where rownum = 1 and did = "+d;
Statement stmt1 = conn.createStatement();
ResultSet rs1 = stmt1.executeQuery(sql1);
while (rs1.next()){
    String jname = rs.getString("jname");

}

 结果集在rs1里面，不是rs。换成 rs1.getString("jname");

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把stmt1 = conn.createStatement() 换成

conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);尝试一下