如何在使用JDBC的SELECT查询中使用动态表名

Question

我有5个表或表要从\查询

我的语法我喜欢这样

String sql2 = "SELECT * FROM ? WHERE Patient_ID = ?";

pst = conn.prepareStatement(sql2);

        System.out.println("SQL before values are set "+sql2);
        System.out.println("The values of table/test name recieved in TestPrint stage 1 "+tblName);
        System.out.println("The values of test name recieved in TestPrint stage 1 "+key);
        // values are outputted correctly but are not getting set in the query

        pst.setString(1, tblName);
        pst.setLong(2, key);
ResultSet rs2 = pst.executeQuery(sql2);

        while(rs2.next()){

            String ID = rs2.getString("ID");

            jLabel35.setText(ID);
            jLabel37.setText(ID);
            jLabel38.setText(ID);
       // them print command is initiated to print the panel
}

问题是，当我运行此命令时，我收到一条错误消息：“ .....您在SQL WHERE Patient_ID =吗？附近有错误？”

当我使用system.out.println（sql2）输出sql时;

值未在sql2中设置

Answer 1

当您准备一条语句时，数据库将构造一个执行计划，如果表不存在，则该计划无法执行。换句话说，Placehodlers只能用于 值
，而不能用于对象名称或保留字。在这种情况下，您将不得不依靠Java来构造您的字符串：

String sql = "SELECT * FROM `" + tblName + "` WHERE Patient_ID = ?";

pst = conn.prepareStatement(sql);
pst.setLong(1, key);
ResultSet rs = pst.executeQuery(sql);