PHP AND子句未显示结果，但OR为

Question

I have a book search that is searching for books i am looking to have it search for books that share authors categories or publishers. I have it set up and it works for the OR clause eg books that have a category CHILDRENS or HISTORY related to them this works correctly but when i search for books that belong to 2 categories (AND) eg CHILDRENS AND MAGIC (Harry Potter) it does not show these book even though they are linked in the database.

Above is the search i have done using OR, When i do a search for books that belong to Childrens AND HISTORY

Above you can see i get no results for books that share Childrens and Magic when Harrypotter books do belong to both of these. Above is the link in the database that gives every book their category, Magic is Category 1 and Childrens is Category 2 and you can see they both share these.

Below is the PHP code for the Query's

<?php
include 'header.php';
include 'searchscriptTEST.php';

$sql =  "SELECT DISTINCT bk.title AS Title, bk.bookid AS BookID, bk.year AS Year, bk.publisher AS Publisher, aut.authorname AS Author 
         FROM book bk 

         JOIN book_category bk_cat 
         ON bk_cat.book_id = bk.bookid

         JOIN categories cat 
         ON cat.id = bk_cat.category_id

         JOIN books_authors bk_aut 
         ON bk_aut.book_id = bk.bookid

         JOIN authors aut
         ON aut.id = bk_aut.author_id";

if(isset($_GET['searchInput'])){
$input = $_GET['searchInput'];
$input = preg_replace('/[^A-Za-z0-9]/', '', $input);
}
if (isset($input)){

    $getters = array();
    $queries = array();

    foreach ($_GET as $key => $value) {
        $temp = is_array($value) ? $value : trim($value);
        if (!empty($temp)){
        if (!in_array($key, $getters)){
            $getters[$key] = $value;
            }
        }
    }

    if (!empty($getters)) {

        foreach($getters as $key => $value){
            //${$key} = $value;
            switch ($key) {
                case 'searchInput':
                    array_push($queries,"(bk.title LIKE '%{$getters['searchInput']}%' 
                    || bk.description LIKE '%{$getters['searchInput']}%' || bk.isbn LIKE '%{$getters['searchInput']}%' 
                    || bk.keywords LIKE '%{$getters['searchInput']}%' || aut.authorname LIKE '%{$getters['searchInput']}%')");
                break;
                case 'srch_publisher':
                    array_push($queries, "(bk.publisher = '{$getters["srch_publisher"]}')");
                break;
                case 'Year':
                    if(isset($getters['Year1']) ==""){
                        array_push($queries, "(bk.year = '{$getters['Year']}')");
                    } else {
                        array_push($queries, "(bk.year BETWEEN '$value' AND '{$getters['Year1']}')");
                    }
                break;
                case 'srch_author':
                     if(isset($getters['authorOperator']) ==""){
                    array_push($queries, "(bk_aut.author_id = '{$getters["srch_author"]}')");
                    } else {
                        $operator = $getters['authorOperator'];
                        array_push($queries, "(bk_aut.author_id = '$value' $operator bk_aut.author_id = '{$getters['srch_author1']}')");
                    }
                break;
                case 'srch_category':
                     if(isset($getters['catOperator']) ==""){
                        array_push($queries, "(bk_cat.category_id = '{$getters["srch_category"]}')");
                    } else {
                        $operator1 = $getters['catOperator'];
                        array_push($queries, "(bk_cat.category_id = '$value' $operator1 bk_cat.category_id = '{$getters['srch_category1']}')");
                    }
                break;

        }
    }
}
if(!empty($queries)){
    $sql .= " WHERE ";
    $i = 1;
    foreach ($queries as $query) {
        if($i < count($queries)){
            $sql .= $query." AND ";
        } else {
            $sql .= $query;
        }   
        $i++;
    }
}
$sql .= " GROUP BY bk.title ORDER BY bk.title ASC";
var_dump($sql);

}else{
    $sql .= " GROUP BY bk.title ORDER BY bk.title ASC";
}


$rs = mysql_query($sql) or die(mysql_error());
$rows = mysql_fetch_assoc($rs);
$tot_rows = mysql_num_rows($rs);
?>

This is the SQL Dump that gets sent to the database,

SELECT
  DISTINCT bk.title AS Title,
  bk.bookid AS BookID,
  bk.year AS Year,
  bk.publisher AS Publisher,
  aut.authorname AS Author 
FROM book bk
  JOIN book_category bk_cat ON bk_cat.book_id = bk.bookid
  JOIN categories cat ON cat.id = bk_cat.category_id
  JOIN books_authors bk_aut ON bk_aut.book_id = bk.bookid
  JOIN authors aut ON aut.id = bk_aut.author_id 
WHERE
  (bk_cat.category_id = '2' AND bk_cat.category_id = '1')
GROUP BY bk.title
ORDER BY bk.title ASC

Answer 1

After formatting your query so that it's actually readable you see the line:

bk_cat.category_id = '2' AND bk_cat.category_id = '1'

That wont work, category_id can not be both 2 and 1 at the same time.

Your query should look something like:

SELECT books.*
FROM books
  JOIN book_categories bc1 ON books.id = bc1.book_id AND bc1.category_id = 1
  JOIN book_categories bc2 ON books.id = bc2.book_id AND bc1.category_id = 2

You need to JOIN twice on categories, or as many times as you have categories to match.

Answer 2

There are multiple ways to do this but the simplist would be to use a WHERE clause something like this to SELECT books which are in more then one category:

WHERE
        `bk`.`book_id` IN (SELECT `book_id` FROM `book_category` WHERE `category_id` = '2')
    AND `bk`.`book_id` IN (SELECT `book_id` FROM `book_category` WHERE `category_id` = '1')