mySQL join three tables and search on several keywords found in one table

Question

I'm trying to limit the size of my database by avoiding multiple records containing the same words and therefore I have build two tables used to relate keyword to rows in other tables.

As an example, we use the follwing search input: "find my"

What is wish go get as a hit, is the product_name from product_id = 106. Could I just search on the product name? No, because the product can be associated with other keywords, that are not part of the product_name.

TABLE: ec_products

product_id    | product_name    | is_deleted
---------------------------------------------
106           | some product    | 0

TABLE: ec_keywords_index

word_id       | keyword
---------------------------------------------
55            | find
61            | my
77            | product

TABLE: ec_keyword_relations

word_id       | application_id    | related_id
------------------------------------------------
55            | 1                 | 106
61            | 1                 | 106
77            | 1                 | 106

So, what I want now when I enter "find my" into my search input is:

• I only want hits where ec_keyword_relations.application_id = 1
• All words in my search string should exist in relation to the product. Eg if i change the search input to "find my pants", we SHOULD NOT find product_id = 106.

Here is what I've tried so far (and I know that I am very far from a working solution at the time being):

    $searchInput = 'find my';
    $keywords = explode(' ', $searchInput);

    $keyword_count = count($keywords);

    $n = 1;
    $query = '';

    foreach($keywords as $keyword) { 
        if ($n !== $keyword_count) { 
            $query_ext = ' AND ';
        } else { 
            $query_ext = ''; 
        } 

        $query .= "(ec_keywords_index.keyword LIKE '%$keyword%')" . $query_ext;

        ++$n;
    }

    $query = "
        SELECT 
            ec_products.product_name

        FROM 
            ec_products

        LEFT JOIN ec_search_word_relations
            ON ec_keyword_relations.related_id = ec_products.product_id

        LEFT JOIN ec_keywords_index
            ON ec_keywords_index.word_id = ec_keyword_relations.word_id

        WHERE 
            ($query) 
        AND 
            ec_products.is_deleted = '0' 
        AND 
            ec_keyword_relations.application_id = '1'

        GROUP BY
            ec_products.product_id

        ORDER BY 
            ec_products.product_name ASC 

        LIMIT 
            100";

    $stmt = $mysqli->prepare($query);
    $stmt->execute();
    $stmt->store_result();
    $stmt->bind_result($name);
    while ($stmt->fetch()) {
        echo $name;
    }

UPDATE:

After some fiddling around, I have come up with this solution which works just as expected. Is it (in terms) of performance a good or a bad solution?

    $searchInput = 'find my';
    $keywords = explode(' ', $searchInput);

    $keyword_count = count($keywords);

    $n = 1;
    $where_query = '';
    $having_query = '';

    foreach($keywords as $keyword) { 
        if ($n != $keyword_count) {
            $w_query_ext = ' OR '; 
            $h_query_ext = ' AND ';
        } else { 
            $w_query_ext = ''; 
            $h_query_ext = ''; 
        }

        $where_query .= "ec_keywords_index.keyword LIKE '%" . $keyword . "%'" . $w_query_ext;

        $having_query .= "related_keywords LIKE '%" . $keyword . "%'" . $h_query_ext;

        ++$n;
    }

    $query = "
        SELECT 
            ec_products.product_name, 
            GROUP_CONCAT(' ', ec_keywords_index.keyword) AS 'related_keywords'

        FROM 
            ec_products, 
            ec_keywords_index

        LEFT JOIN 
            ec_keyword_relations 
            ON ec_keyword_relations.word_id = ec_keywords_index.word_id

        WHERE ($where_query) 
            AND ec_products.product_id = ec_keyword_relations.related_id 
            AND ec_keyword_relations.application_id = '1' 
            AND ec_products.is_deleted = '0'

        GROUP BY 
            ec_products.product_name

        HAVING 
            ($having_query)

        LIMIT 
            100";

    $stmt = $mysqli->prepare($query);
    $stmt->execute();
    $stmt->store_result();
    $stmt->bind_result($name);
    while ($stmt->fetch()) {
        echo $name;
    }

The above example outputs a query like this:

    SELECT 
        ec_products.product_name, 
        GROUP_CONCAT(' ', ec_keywords_index.keyword) AS 'related_keywords'

    FROM 
        ec_products, 
        ec_keywords_index

    LEFT JOIN 
        ec_keyword_relations 
        ON ec_keyword_relations.word_id = ec_keywords_index.word_id

    WHERE (ec_keywords_index.keyword LIKE '%find%' OR ec_keywords_index.keyword LIKE '%my%') 
        AND ec_products.product_id = ec_keyword_relations.related_id 
        AND ec_keyword_relations.application_id = '1' 
        AND ec_products.is_deleted = '0'

    GROUP BY 
        ec_products.product_name

    HAVING 
        (related_keywords LIKE '%find%' AND related_keywords LIKE '%my%')

    LIMIT 
        100

I'm using GROUP_CONCAT to create a column containing all the keywords related to the products, then my WHERE clause is used to ONLY select the keywords that are actually found in my search string... Then the HAVING clause is used to search in column build using GROUP_CONCAT.

Answer 1

OWN ANSWER WITH EXAMPLE:

After some fiddling around, I have come up with this solution which works just as expected. I don't know if it is best practice, but it works like a charm.

    $searchInput = 'find my';
    $keywords = explode(' ', $searchInput);

    $keyword_count = count($keywords);

    $n = 1;
    $where_query = '';
    $having_query = '';

    foreach($keywords as $keyword) { 
        if ($n != $keyword_count) {
            $w_query_ext = ' OR '; 
            $h_query_ext = ' AND ';
        } else { 
            $w_query_ext = ''; 
            $h_query_ext = ''; 
        }

        $where_query .= "ec_keywords_index.keyword LIKE '%" . $keyword . "%'" . $w_query_ext;

        $having_query .= "related_keywords LIKE '%" . $keyword . "%'" . $h_query_ext;

        ++$n;
    }

    $query = "
        SELECT 
            ec_products.product_name, 
            GROUP_CONCAT(' ', ec_keywords_index.keyword) AS 'related_keywords'

        FROM 
            ec_products, 
            ec_keywords_index

        LEFT JOIN 
            ec_keyword_relations 
            ON ec_keyword_relations.word_id = ec_keywords_index.word_id

        WHERE ($where_query) 
            AND ec_products.product_id = ec_keyword_relations.related_id 
            AND ec_keyword_relations.application_id = '1' 
            AND ec_products.is_deleted = '0'

        GROUP BY 
            ec_products.product_name

        HAVING 
            ($having_query)

        LIMIT 
            100";

    $stmt = $mysqli->prepare($query);
    $stmt->execute();
    $stmt->store_result();
    $stmt->bind_result($name);
    while ($stmt->fetch()) {
        echo $name;
    }

The above example outputs a query like this:

    SELECT 
        ec_products.product_name, 
        GROUP_CONCAT(' ', ec_keywords_index.keyword) AS 'related_keywords'

    FROM 
        ec_products, 
        ec_keywords_index

    LEFT JOIN 
        ec_keyword_relations 
        ON ec_keyword_relations.word_id = ec_keywords_index.word_id

    WHERE (ec_keywords_index.keyword LIKE '%find%' OR ec_keywords_index.keyword LIKE '%my%') 
        AND ec_products.product_id = ec_keyword_relations.related_id 
        AND ec_keyword_relations.application_id = '1' 
        AND ec_products.is_deleted = '0'

    GROUP BY 
        ec_products.product_name

    HAVING 
        (related_keywords LIKE '%find%' AND related_keywords LIKE '%my%')

    LIMIT 
        100

I'm using GROUP_CONCAT to create a column containing all the keywords related to the products, then my WHERE clause is used to ONLY select the keywords that are actually found in my search string... Then the HAVING clause is used to search in column build using GROUP_CONCAT.