Question

我有书籍和作者的数据库。这两个实体之间的关系是多对多的，所以它们之间有一个联合表。

books主要books.book_id，主要authors.author_id为主要，联合表book_authors包含：book_authors.book_id和book_authors.author_id。
每本书都有多位作者。

我想要做的是拥有一个php页面，然后在一行中显示每本书，它说：author1：....，author2（如果适用）

我希望我的php看起来有点像：

Book Name: THE BOOK NAME
Author(s): joe- John- Sara

我使用了以下代码，问题是它返回单个结果。因此，如果book1由多位作者创作，则每次与不同的作者一起展示不止一次。我想做的是让每本书都跟着一系列作者

<html>
<body>

<?php
$con = mysql_connect("localhost","myusername","mypassword");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }

mysql_select_db("mydb", $con);

$result1 = mysql_query("
    SELECT books.title, authors.fname, authors.lname 
    FROM books, book_authors, authors  
    WHERE books.book_id = book_authors.book_id 
    AND authors.author_id=book_authors.author_id");


while($row = mysql_fetch_array($result1))
  {
print "<h3>Book Name:</h3>";
  echo $row ['title'];
print "<br />";
print "Author(s):";
  echo $row ['fname'];
  echo $row ['lname'];
  echo "<br />";
  }

mysql_close($con);
?>

</body>
</html>

Answer 1

这是一个应该解决问题的查询：

SELECT books.title, authors.fname, authors.lname FROM books LEFT JOIN
book_authors ON books.book_id = book_authors.book_id LEFT JOIN authors
ON authors.author_id = book_authors.author_id

您必须仔细检查行作者的book_id是否相同。

另一种方法是首先选择书籍，然后在你的foreach循环中，通过book_authors表查找该书的作者。

需要注意的另一件事是，mysql_* 函数已弃用，您应该考虑使用mysqli_*或PDO。

Answer 2

您的SQL查询不正确。它需要像这样形成。

SELECT column_name(s) FROM table_name1 INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name

SELECT books.title, authors.fname, authors.lname FROM books INNER JOIN authors ON books.book_id = authors.book_id

SELECT Persons.LastName，Persons.FirstName，Orders.OrderNo 来自人内部联合订单 ON Persons.P_Id = Orders.P_Id ORDER BY Persons.LastName

Answer 3

尝试group_concat

SELECT books.title, group_concat(concat(authors.fname,' ',authors.lname) AS Authors
FROM books, book_authors, authors  
WHERE books.book_id = book_authors.book_id 
AND authors.author_id=book_authors.author_id
GROUP BY books.title

然后在PHP中

  while($row = mysql_fetch_array($result1))
  {
     print "<h3>Book Name:</h3>";
     echo $row ['title'];
     print "<br />";
     $authors = explode($row['Authors']); //array of authors

     for($authors as $author)
     {
        echo($author.'<br/>')
     }
   }

您可以使用JOIN

SELECT books.title, GROUP_CONCAT(authors.fname) AS Authors 
FROM books
LEFT JOIN book_authors ON books.book_id = book_authors.book_id
LEFT JOIN authors ON book_authors.author_id = authors.author_id
GROUP BY books.title

php mysql数组结果问题

3 个答案: