MY PLATFORM:
PHP & mySQL
WHAT I HAVE HERE:
I have 4 tables, namely, ‘books’, ‘book_type’, ‘book_categories’, ‘all_categories’.
WHAT I AM TRYING TO DO:
In simple words, I want to display all the books that are in stock i.e. in_stock = ‘y’, with all the book related information from all the tables, only once without repeating the entries. Currently the each of the books are repeated and I want to show them only once.
THE CURRENT PROBLEM:
In the frontend within my app., the entries are shown repeatedly when in fact when I am expecting them to show up only once (as in DISTINCT / UNIQUE) and not repeat themselves.
MY SUSPICION:
I suspect that the repeating data is because of the categories that each of the books belong to. Every single book entry is shown as many times, as it belongs to a category. Confusing? I mean that if a book1 belongs to 4 categories, then book1 is shown 4 times. If book2 belong to 2 categories, then it is shown 2 times.
WHAT I NEED:
I need the PHP & mySQL code that would solve the above problem. I am hoping that we can solve the problem without using GROUP_CONCAT in mySQL as there’s a limit (1024 ?) for the same. A book can belong to many categories and I do not want to risk losing any data by using GROUP_CONCAT. I would also like to do this in a single query without accessing the database repeatedly in a loop. Thanks for understanding.
All the tables and the corresponding data to replicate the problem are as follows:
CREATE TABLE IF NOT EXISTS `books` (
`book_id` int(11) NOT NULL auto_increment,
`book_type_id` int(11) NOT NULL,
`book_title` varchar(50) NOT NULL,
`book_price` smallint(4) NOT NULL,
`in_stock` char(1) NOT NULL,
PRIMARY KEY (`book_id`),
KEY `book_type_id` (`book_type_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
--
-- Dumping data for table `books`
--
INSERT INTO `books` (`book_id`, `book_type_id`, `book_title`, `book_price`, `in_stock`) VALUES
(1, 1, 'My Book 1', 10, 'y'),
(2, 1, 'My Book 2', 20, 'n'),
(3, 2, 'My Book 3', 30, 'y'),
(4, 3, 'My Book 4', 40, 'y'),
(5, 2, 'My Book 5', 50, 'n'),
(6, 1, 'My Book 6', 60, 'y'),
(7, 3, 'My Book 7', 70, 'n'),
(8, 2, 'My Book 8', 80, 'n'),
(9, 1, 'My Book 9', 90, 'y'),
(10, 3, 'My Book 10', 100, 'n');
--
-- Table structure for table `book_type`
--
CREATE TABLE IF NOT EXISTS `book_type` (
`book_type_id` int(11) NOT NULL auto_increment,
`book_type` varchar(50) NOT NULL,
PRIMARY KEY (`book_type_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
--
-- Dumping data for table `book_type`
--
INSERT INTO `book_type` (`book_type_id`, `book_type`) VALUES
(1, 'Good'),
(2, 'Better'),
(3, 'Best');
--
-- Table structure for table `book_categories`
--
CREATE TABLE IF NOT EXISTS `book_categories` (
`book_id` int(11) NOT NULL,
`cat_id` int(11) NOT NULL,
PRIMARY KEY (`book_id`,`cat_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
--
-- Dumping data for table `book_categories`
--
INSERT INTO `book_categories` (`book_id`, `cat_id`) VALUES
(1, 1),
(1, 2),
(1, 3),
(1, 4),
(1, 5),
(2, 1),
(2, 2),
(3, 1),
(3, 2),
(3, 3);
--
-- Table structure for table `all_categories`
--
CREATE TABLE IF NOT EXISTS `all_categories` (
`cat_id` int(11) NOT NULL auto_increment,
`category` varchar(50) NOT NULL,
PRIMARY KEY (`cat_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
--
-- Dumping data for table `all_categories`
--
INSERT INTO `all_categories` (`cat_id`, `category`) VALUES
(1, 'Comedy'),
(2, 'Drama'),
(3, 'Romance'),
(4, 'Horror'),
(5, 'Trivia'),
(6, 'Puzzles'),
(7, 'Riddles'),
(8, 'Kids'),
(9, 'Gents'),
(10, 'Ladies');
MY TARGET:
//MY QUERY:
SELECT books.book_title, books.book_price,
book_type.book_type,
all_categories.category
FROM books
LEFT JOIN book_type ON books.book_type_id = book_type.book_type_id
LEFT JOIN book_categories ON books.book_id = book_categories.book_id
LEFT JOIN all_categories ON book_categories.cat_id = all_categories.cat_id
WHERE books.in_stock = 'y'
CURRENT OUTPUT:
book_title book_price book_type category
My Book 1 10 Good Comedy
My Book 1 10 Good Drama
My Book 1 10 Good Romance
My Book 1 10 Good Horror
My Book 1 10 Good Trivia
My Book 3 30 Better Comedy
My Book 3 30 Better Drama
My Book 3 30 Better Romance
My Book 4 40 Best NULL
My Book 6 60 Good NULL
My Book 9 90 Good NULL
NEED THE FOLLOWING OUTPUT:
book_title book_price book_type category
My Book 1 10 Good Comedy, Drama, Romance, Horror, Trivia
My Book 3 30 Better Comedy, Drama, Romance
My Book 4 40 Best NULL
My Book 6 60 Good NULL
My Book 9 90 Good NULL
Thanks to all in advance.
Best way to make sure you don’t lose ANY data would be multiple queries. Query the tables seperately and join them in PHP, probably so your queries look like this
etc
Edit:
No, you shouldn’t need 100 hits on the DB, just two, one to get the books, the next to get the categories. The looping would be done in PHP to loop through the second query and join the data with the first. The second query could be
SELECT book.book_id, all_categories.category FROM book_category JOIN all_categories on book_categories.cat_id=all_categories.cat_id JOIN books on books.book_id=book_categories.book_id WHERE books.in_stock= ‘y’;
OR