Question

Statement stmt = null;

    String query = "SELECT CarLot.CAR.Make, CarLot.CAR.Model, CarLot.CAR.Year, CarLot.CAR.Sold_Status, CarLot.OWNER.First_Name,CarLot.OWNER.Last_Name"+
            "FROM CarLot.CAR, CarLot.OWNER" +
                    " WHERE CarLot.CAR.Sold_Status = TRUE";

    try {
        con = getConnection();
        stmt = con.createStatement();

        ResultSet rs = stmt.executeQuery(query);

         String heading1 = "    Make"; String heading2 = "    Model"; String
         heading3 = "    Year"; String heading4="Sold Status";
         System.out.printf("%-20s %-20s %-20s %-20s\n", heading1, heading2,
         heading3,heading4);
         System.out.println("--------------------------------------------------------------------------\n");

        while (rs.next()) {

            String make = rs.getString("car.Make");
            String model = rs.getString("car.Model");
            int carYear = rs.getInt("car.Year");
            boolean soldStatus = rs.getBoolean("car.Sold_Status");
            String firstName = rs.getString("owner.First_Name");

            System.out.printf("%-2s %-20s %-20s %-20s %-20s\n", 
              make, model, carYear,soldStatus,firstName);

             }
        System.out.println("\n\n");
    } finally {
        stmt.close();

    }

我遇到的问题是SQL语法错误，该语法在MySql workbench 6.0中有效但在我的Java App中无法通过JDBC工作，我是SQl和JDBC的新手，我意识到我的结果集可能不是100％这个查询也可能是问题，它来自一个共享方法，在这种情况下我更关心SQL查询语句。

Answer 1

问题是您在最后选择的列名与FROM之间缺少空格。要解释您的查询，您有：

String query = "SELECT ..., CarLot.OWNER.Last_Name"+ // oops, no space!
        "FROM CarLot.CAR, CarLot.OWNER" +
         " WHERE CarLot.CAR.Sold_Status = TRUE";

这个错误很常见，因为在一行的末尾很难看到丢失的空格，但是有一种代码风格用于解决这个问题 - 我在 start 中添加了空格该行，如下：

String query = "SELECT CarLot.CAR.Make, CarLot.CAR.Model, CarLot.CAR.Year, CarLot.CAR.Sold_Status, CarLot.OWNER.First_Name,CarLot.OWNER.Last_Name"+
    " FROM CarLot.CAR, CarLot.OWNER" +
    " WHERE CarLot.CAR.Sold_Status = TRUE";

每一行都以quote-space开头，即" ...，所以现在当一个换行的字符串缺少一个空格时非常明显，而且因为SQL（通常）空白不敏感，你可以在最终也没有造成任何问题。

Answer 2

在FROM子句

之前添加空格

String query = "SELECT CarLot.CAR.Make, CarLot.CAR.Model, CarLot.CAR.Year, CarLot.CAR.Sold_Status, CarLot.OWNER.First_Name,CarLot.OWNER.Last_Name" +
           " FROM CarLot.CAR, CarLot.OWNER" +
                    " WHERE CarLot.CAR.Sold_Status = TRUE";

除此之外：考虑使用PreparedStatement来防范SQL injection攻击

Answer 3

查询的第一行和第二行之间没有空格，因此您有select ... CarLot.OWNER.Last_NameFROM CarLot ....添加空间，看看会发生什么。

使用JDBC的JAVA中的SQL语法

3 个答案: