SQL 使用 java servlet 时出现无效列错误

Question

这是我的主页

Main_page

出于某种原因，我可以按标题搜索列表，但无法获取所有列表。正如我已经检查过的那样，按钮参数是可读的。这是我在 servlet 中获取所有书籍列表的代码：

searchResults = bookDao.loadBookFromDB();
System.out.println("\nGet all book: ");
bookDao.showList(searchResults);

这是我获取所有书籍的代码：

public ArrayList<BookDTO> loadBookFromDB() throws SQLException, NamingException {
    try {
        connection = MyDB.createConnection();
        if (connection != null) {
            String sql = "Select Id, Title, Author, ImageUrl, Quantity, Price, CategoryId, CreatedDate, Status"
                    + "From " + MyConstants.TBL_BOOK
                    + " Where Quantity >= ? "
                    + " And Status = " + MyConstants.STATUS_STRING_ACTIVE;

            statement = connection.prepareStatement(sql);
            statement.setInt(1, MyConstants.MIN_BOOK_QUANTITY);

            result = statement.executeQuery();

            ArrayList<BookDTO> searchResult = null;
            while (result.next()) {
                String title = result.getString("Title");
                String author = result.getString("Author");
                String imageUrl = result.getString("ImageUrl");
                String status = result.getString("Status");
                int id = result.getInt("Id");
                int price = result.getInt("Price");
                int quantity = result.getInt("Quantity");
                int categoryId = result.getInt("CategoryId");
                Date createDate = result.getDate("CreatedDate");
                if (searchResult == null) {
                    searchResult = new ArrayList<>();
                }
                searchResult.add(new BookDTO(id, categoryId, quantity, price, title, author, status, imageUrl, createDate));
            }
            return searchResult;
        }
    } finally {
        checkConnection();
    }
    return MyConstants.FOUND_NO_LIST;
}

这是我按标题代码搜索的图书：

public ArrayList<BookDTO> getBookByLikeTitle(String searchValue) throws SQLException, NamingException {
    try {
        connection = MyDB.createConnection();
        if (connection != null) {
            String sql = "Select Id, Title, Author, ImageUrl, Quantity, Price, CategoryId, CreatedDate, Status "
                    + "From " + MyConstants.TBL_BOOK
                    + "Where Title like ?";

            statement = connection.prepareStatement(sql);
            statement.setString(1, "%" + searchValue + "%");

            result = statement.executeQuery();

            ArrayList<BookDTO> searchResult = null;
            while (result.next()) {
                String title = result.getString("Title");
                String author = result.getString("Author");
                String imageUrl = result.getString("ImageUrl");
                String status = result.getString("Status");
                int id = result.getInt("Id");
                int price = result.getInt("Price");
                int quantity = result.getInt("Quantity");
                int categoryId = result.getInt("CategoryId");
                Date createDate = result.getDate("CreatedDate");
                if (searchResult == null) {
                    searchResult = new ArrayList<>();
                }
                searchResult.add(new BookDTO(id, categoryId, quantity, price, title, author, status, imageUrl, createDate));
            }
            return searchResult;
        }
    } finally {
        checkConnection();
    }
    return MyConstants.FOUND_NO_LIST;
}

这是我的常量：

public final static String TBL_BOOK = "Book ";
public final static String STATUS_STRING_ACTIVE = "Active";
public final static int MIN_BOOK_QUANTITY = 1;

我展示的是标题一，因为该代码非常好。那么可以看到，两种方法中的结果集部分是完全一样的，所以结果部分没有问题。所以，我去检查了数据库。这是我的 table 创建：

Create table [Book] (
[Id] int NOT NULL IDENTITY(1,1) primary key,
[Title] varchar(200),
[Author] varchar(50),
[ImageUrl] varchar(MAX),
[Quantity] int,
[Price] int,
[CategoryId] int,
[CreatedDate] datetime,
[Status] varchar(10))

而且我的SQL查询没有错check_get_all_query。因此，我只能认为错误的部分是 Quantity 条件部分。所以，我尝试将值直接放在字符串中而不是使用 setInt 语句：

String sql = "Select Id, Title, Author,ImageUrl, Quantity, Price, CategoryId, CreatedDate, Status"
           + "From " + MyConstants.TBL_BOOK
           + "Where Quantity >= " + MyConstants.MIN_BOOK_QUANTITY 
           + "And Status = " + MyConstants.STATUS_STRING_ACTIVE;

statement = connection.prepareStatement(sql);

结果是一样的。所以...我卡住了。日志一直显示我有这个错误：

BookMarketController SQL: Invalid column name 'Quantity'.

谁能告诉我为什么？

Answer 1

您在 Status" 之后错过了一个 space，因此有一个 StatusFrom 列。

在后续行的开头使用绑定变量和 space：

String selectAll =
"Select Id, Title, Author,ImageUrl, Quantity, Price, CategoryId, CreatedDate, Status";
String sql = selectAll  
       + " Where Quantity >= ? And Status = ?";

SQL 使用 java servlet 时出现无效列错误

SQL Error Invalid column when using java servlet

java

sql

sql-server

servlets