如何用3表创建内部联接

Question

mysql> SELECT * FROM main_table;
+--------+----------+--------+
| id_book | id_author      |description |
+--------+----------+--------+
| 1           | 101     |   I love cat |
+--------+----------+--------+

mysql> SELECT * FROM author;
+---------+-----------+
|  id_author | name_author |
+---------+-----------+
| 101     | Dr Sent     |
+---------+-----------+

mysql> SELECT * FROM book;
+--------+---------+
| id_book | name_book |
+--------+---------+
|      1 |     cat |
+--------+---------+

hello I am still new in PHP now im bit confuse with PHP and MySQL. I have a drop drown list which is related to one of my table in database.

firstly my system appear a page of list author's name and user will able to choose which one user like.

 JK ROWLING 
 DR SEUSS <-- author_name
 ROAD DAHL

Next, it will go to a new page and have a select(list/menu) which show a list of BOOK NAME. I can retrieve the dropdown list from database, but my problem is when I select one of BOOK NAME in the dropdown, it show all book description and cannot select the right description.

here is my coding to make it more clear

$currentPage = $_SERVER["PHP_SELF"];

mysql_select_db($database_config, $config);
$query_Recordset1 = "SELECT * FROM book ORDER BY name_book ASC";
$Recordset1 = mysql_query($query_Recordset1, $config) or die(mysql_error());
$row_Recordset1 = mysql_fetch_assoc($Recordset1);
$totalRows_Recordset1 = mysql_num_rows($Recordset1);

$maxRows_Recordset2 = 1;
$pageNum_Recordset2 = 0;
if (isset($_GET['pageNum_Recordset2'])) {
  $pageNum_Recordset2 = $_GET['pageNum_Recordset2'];
}
$startRow_Recordset2 = $pageNum_Recordset2 * $maxRows_Recordset2;

$colname_Recordset2 = "-1";
if (isset($_GET['id_book'])) {
  $colname_Recordset2 = $_GET['id_book'];
}
mysql_select_db($database_config, $config);
$query_Recordset2 = sprintf("SELECT * FROM main_table WHERE id_book = %s ORDER BY description ASC", GetSQLValueString($colname_Recordset2, "int"));
$query_limit_Recordset2 = sprintf("%s LIMIT %d, %d", $query_Recordset2, $startRow_Recordset2, $maxRows_Recordset2);
$Recordset2 = mysql_query($query_limit_Recordset2, $config) or die(mysql_error());
$row_Recordset2 = mysql_fetch_assoc($Recordset2);

if (isset($_GET['totalRows_Recordset2'])) {
  $totalRows_Recordset2 = $_GET['totalRows_Recordset2'];
} else {
  $all_Recordset2 = mysql_query($query_Recordset2);
  $totalRows_Recordset2 = mysql_num_rows($all_Recordset2);
}
$totalPages_Recordset2 = ceil($totalRows_Recordset2/$maxRows_Recordset2)-1;

$queryString_Recordset2 = "";
if (!empty($_SERVER['QUERY_STRING'])) {
  $params = explode("&", $_SERVER['QUERY_STRING']);
  $newParams = array();
  foreach ($params as $param) {
    if (stristr($param, "pageNum_Recordset2") == false && 
        stristr($param, "totalRows_Recordset2") == false) {
      array_push($newParams, $param);
    }
  }
  if (count($newParams) != 0) {
    $queryString_Recordset2 = "&" . htmlentities(implode("&", $newParams));
  }
}
$queryString_Recordset2 = sprintf("&totalRows_Recordset2=%d%s", $totalRows_Recordset2, $queryString_Recordset2);

Answer 1

Try This.........

SELECT 
    a.*, b.*, c.* 
FROM main_table a 
    inner join author b on a.id_author = b.id_author 
    inner join book c on a.id_book = c.id_book

Answer 2

First off, I'd recommend using AJAX and staying on the same page when an item is selected. By this you can separate the code for the different input boxes and it'll look better at the end of the day.

To answer your question, here's the SQL Statement for mySQL you should run to get what you asked for:

SELECT MAT.*,AUT.name_author, BOO.name_book
FROM main_table AS MAT, author AS AUT, book AS BOO
WHERE (MAT.id_book=BOO.id_book AND MAT.id_author=AUT.id_author) AND MAT.id_author=101
ORDER BY MAT.id_author, MAT.id_book;

You can find the SQL Fiddle code for the above guy here . You can update the "filtering" in the WHERE clause to filter by another table's author ID or by book ID