Question

我为学校项目建立了这个网站，它似乎没有检索数据。我一直在寻找AGES并且无法找出它为什么没有检索。 SQL有时可以在phpMyAdmin中运行，但从不在界面中运行。

<?php

$con=mysqli_connect("localhost","root","#","book_catalogue");

{
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
?>
<div id="wrapper">
    <div id="left-col">
        <img src="images/left-img.png" alt="books" />
    </div>
    <div id="header">
        <h1>BOOK CATALOGUE</h1>
    </div>

    <!--Radio buttons that allow user to select the search criteria-->
    <div id="navigation">
        <form name="input" action="indexV4.php" method="get">
                SEARCH BY: ALL<input type="radio" name="books" value="ALL" checked>
                TITLE<input type="radio" name="books" value="TITLE">
                AUTHOR<input type="radio" name="books" value="AUTHOR">
                GENRE<input type="radio" name="books" value="GENRE">
                BOOK TYPE<input type="radio" name="books" value="BOOKTYPE"> 
                <input type="text" name="SEARCH" value="SEARCH">
                <input type="submit" value="GO">
        </form>
    </div>
            <?php
            $Books = $_GET['books'];
            $Search = $_GET['SEARCH'];
                //if the radio button 'TITLE' is selected, this query will run
                if($Books=='TITLE')
                    {
                        $result = mysqli_query($con,"
                        SELECT tbl_books.ISBN, tbl_books.Title, tbl_books.Author, tbl_books.Book_Image, tbl_book_type.Name, tbl_categories.Name FROM tbl_books, tbl_book_type, tbl_categories WHERE (tbl_books.Type_id = tbl_book_type.Type_id) AND (tbl_books.Category_id = tbl_categories.Category_id)
                        WHERE tbl_books.Title LIKE '%$Search%'");
                    }
                    //if the radio button 'AUTHOR' is selected, this query will run
                else if ($Books=='AUTHOR')
                    {
                        $result = mysqli_query($con,"
                        SELECT tbl_books.ISBN, tbl_books.Title, tbl_books.Author, tbl_books.Book_Image, tbl_book_type.Name, tbl_categories.Name FROM tbl_books, tbl_book_type, tbl_categories
                        WHERE (tbl_books.Type_id = tbl_book_type.Type_id) AND (tbl_books.Category_id = tbl_categories.Category_id)
                        WHERE tbl_books.Author LIKE '%$Search%'");
                    }
                    //if the radio button 'GENRE' is selected, this query will run
                else if ($Books=='GENRE')
                    {
                        $result = mysqli_query($con,"
                        SELECT tbl_books.ISBN, tbl_books.Title, tbl_books.Author, tbl_books.Book_Image, tbl_books.Type_id, tbl_books.Category_id FROM tbl_books
                        WHERE tbl_books.Author LIKE '%$Search%'");
                    }
                    //if the radio button 'BOOK TYPE' is selected, this query will run
                else if ($Books=='BOOKTYPE')
                    {
                        $result = mysqli_query($con,"
                        SELECT tbl_books.ISBN, tbl_books.Title, tbl_books.Author, tbl_books.Book_Image, tbl_book_type.Name, tbl_categories.Name FROM tbl_books, tbl_book_type, tbl_categories 
                        WHERE (tbl_books.Type_id = tbl_book_type.Type_id) AND (tbl_books.Category_id = tbl_categories.Category_id)
                        WHERE tbl_book_type.Name LIKE '%$Search%'");
                    }
                    //if 'ALL' is selected, this query will run
                else 
                {
                    $result = mysqli_query($con, "
                    SELECT tbl_books.ISBN, tbl_books.Title, tbl_book_type.Name, tbl_categories.Name FROM tbl_books, tbl_book_type, tbl_categories WHERE (tbl_books.Type_id = tbl_book_type.Type_id) AND (tbl_books.Category_id = tbl_categories.Category_id)
                    WHERE tbl_books.Title OR tbl_books.Author OR tbl_categories.Name OR tbl_book_type.Name LIKE '%$Search%'");
                }
            //while it is retrieving the data, echo it onto the screen
     while($row = mysqli_fetch_array($result,MYSQLI_BOTH))
     {
            ?>
    </div>
    <div id="content">
    <!--Display of search results-->

        <div class="books">
            <img src="book-covers/<?php echo $row['Book_Image']; ?>" alt="<?php echo $row['Title']; ?>" />
            <p class="first"><?php echo $row['Title']; ?></p>
            <p><?php echo $row['Author']; ?></p>
            <p><?php echo $row['ISBN']; ?></p>
            <p><?php echo $row['Type_id']; ?></p>
            <p><?php echo $row['Category_id']; ?></p>
        </div>
    </div>
    <?php
    //close the loop
    }
    ?>
</div>

Answer 1

您的查询开头不正确。在一个语句中不能有两个WHERE。以下是您的查询语句之一

SELECT tbl_books.ISBN, tbl_books.Title, 
       tbl_books.Author, tbl_books.Book_Image, 
       tbl_book_type.Name, tbl_categories.Name 
FROM tbl_books, tbl_book_type, tbl_categories
WHERE (tbl_books.Type_id = tbl_book_type.Type_id) AND 
      (tbl_books.Category_id = tbl_categories.Category_id)
WHERE tbl_books.Title LIKE '%$Search%'

您是否看到两次使用WHERE？

此外，您的代码不安全。您应该使用PDO或至少使用mysql_real_escape_string。

Answer 2

正如invisal所说，你不能在一个陈述中有2个WHERE。

我建议更改你的if语句内容。而不是mysqli_query($con, "SELECT BLA BLA");

这样做：

$ sql =“SELECT BLA BLA”;

然后，在if语句创建$ sql之后，执行以下操作：

$result = mysql_query($con,$sql);

if($result === false) {
  echo 'Error in query [' . $sql . ']' . "\n" . 'Error: ' . mysql_error();
}

然后你会看到你的查询有什么问题。

编辑：让我试着让这个更清楚：

if($Books=='TITLE')
                    {
                        $sql = "SELECT tbl_books.ISBN, tbl_books.Title, tbl_books.Author, tbl_books.Book_Image, tbl_book_type.Name, tbl_categories.Name FROM tbl_books, tbl_book_type, tbl_categories WHERE (tbl_books.Type_id = tbl_book_type.Type_id) AND (tbl_books.Category_id = tbl_categories.Category_id)
                        WHERE tbl_books.Title LIKE '%$Search%'";
                    }

将所有if / else if语句更改为如此。您正在做的是使用if语句来决定变量$sql;

将包含哪个查询

然后，在所有if语句之后，您可以发送$sql查询，如上所示。如果您的查询中存在错误，if($result === false)部分会将mysql的投诉输出到您的屏幕，这可以帮助您调试查询。

数据库检索系统

2 个答案: