select book1.书号,book1.书名,book1.作者,book2.类别 from book1,book2 where book1.书号=book2.书号 and book2.类别='某个值'或
select book1.*,book2.类别 from book1,book2 where book1.书号=book2.书号 and book2.类别='某个值'
select book1.*,book2.类别 from book1,book2 where book1.书号=book2.书号 and book2.类别='某个值'
$result=mysql_query("select * from book1 where book1.book_id=book2.book_id add book2.book_category=$book_category");
$myrow = mysql_fetch_array($result);
$numrows=mysql_num_rows($result);
有错误提示如下
Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in /home/EdiorWeb/www.goldmay.com/html/book1/list.php on line 7Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/EdiorWeb/www.goldmay.com/html/book1/list.php on line 8其中book_category由表单提交获得
book_id book_name book_author book_content
1001 围城
1002 冬天表book2
booi_id book_category
1001 小说
1002 小说
$result=mysql_query("select count(*) from book1,book2 where book1.book_id=book2.book_id and book2.book_category='$book_category'");
$myrow = mysql_fetch_array($result);
$numrows=mysql_num_rows($result);
echo $numrows;前面这段语句所要达到的目的是输出是 小说 类的所有图书的信息
分析应该输出2
可程序执行结果为1
不知到错在哪里,正确的该怎么写?
$result=mysql_query("select * from book1,book2 where book1.book_id=book2.book_id and book2.book_category='$book_category'");
也就是说用count会在第一次满足where条件的时候停止继续查找。
不知道我说明白了吗?