Long nested SELECT statement

[dbewick123]

Ok, I am trying to do some camparisons in my tables and return results based on weather values match... i'll post the code then explain it, I think it will be easier that way

 

/* the below method works and returns all the desired tags */

 

 

$tags = mysql_query("SELECT `tag1`, `tag2`, `tag3`, `tag4`, `tag5` FROM `books` WHERE `book_id` IN (SELECT `book_id` FROM `userBooks` WHERE `user_id` = '$sessionUserId')");

 

/* this is the method i am struggling with, I am trying to SELECT the book info (auther etc.) from the books table WHERE the $tags (from previous query, match any tags of other books in the `books` table. */

 

$recommended =mysql_query("SELECT `auther`, `title`, `isbn` FROM `books`  

WHERE `$tags` = (SELECT `tag1`, `tag2`, `tag3`, `tag4`, `tag5` from `books` WHERE  `book_id` NOT IN (SELECT `book_id` FROM `userBooks` WHERE `user_id` = '$sessionUserId'))");

 

the way i interpret this query is that it will SELECT the `auther` `title` etc. from the books table where the $tags = the tags in the `books` table WHERE book_id is not already in the `userBooks` table against that `user_id` - this obviously isnt happending because nothing is being returned.

 

Please can someone help/advise me with this?

 

Thanks 

 

Dbewick123

[Barand]

Correctly normalize those tags into another table then come back and we can help you.

[dbewick123]

Correctly normalize those tags into another table then come back and we can help you.

I've been reading up on normalizing databases and 1NF, 2NF and 3NF to a point where im fairly sure i understand it, however i'm unclear as to what you are telling me to do.... are you saying that i should put these tags into a seperate database table with the specific user id as a primary key :/ ?? 

[Barand]

As the tags belong to a book, why would you use the the user_id?

 

Table book_tag:

 

book_id INT

tag_id  INT

PRIMARY KEY (book_id, tag_id)

 

Table tag:

 

tag_id INT PK

tag_value VARCHAR(nn)