java - 设置字符串时出现 MySQLSyntaxErrorException

Question

我有一个奇怪的问题。当我在以下代码段中执行查询时，它会抛出 MySQLSyntaxErrorException 并显示以下消息:

You have an error in your SQL syntax; check the manual that corresponds to your 
MySQL server version for the right syntax to use near 
''fantasy' SET Quantity = 3 WHERE BookName = 'The Silmarilion'' at line 1

代码:

private void updateDBTable(String category, Vector dataVector) {
    try {  
        for(int i = 0; i < dataVector.size(); i++) {

            String bookName = String.valueOf(((Vector) dataVector.elementAt(i))
                                  .elementAt(0));
            int quantity = (int) ((Vector) dataVector.elementAt(i))
                                  .elementAt(4);               

            statement = databaseConnection
              .prepareStatement("UPDATE ? SET Quantity = ? WHERE BookName = ?");   
            statement.setString(1, category);
            statement.setInt(2, quantity);
            statement.setString(3, bookName);
            statement.executeUpdate();
        }
    }

但是如果我这样写:

private void updateDBTable(String category, Vector dataVector) {
    try {  
        for(int i = 0; i < dataVector.size(); i++) {

            String bookName = String.valueOf(((Vector) dataVector.elementAt(i))
                                        .elementAt(0));
            bookName = "'" + bookName + "'";
            int quantity = (int) ((Vector) dataVector.elementAt(i))
                                        .elementAt(4);               

            statement = databaseConnection
               .prepareStatement("UPDATE " + 
                                  category + 
                                 " SET Quantity = ? WHERE BookName = " + 
                                 bookName);   
            statement.setInt(1, quantity);
            statement.executeUpdate();
        }
    }

效果很好。你能帮我找出为什么第一个例子中的语法是错误的吗？

Answer 1

在第一种情况下，您还提供了表名称作为参数。准备好的语句将列名作为参数。使用prepareStatement时需要在语句中提供表名