Search query for multiple tables with count(*)? - php

Question

I have a search field for an online shop that uses MySQL query for 2 different tables. The first table is vinyls which has 13 columns, and the second table is products which has 10 columns. The result I want is that if you enter a keyword, it will search the album_name and artist_name columns of table vinyls, and the name column in table products to find any matches.
My php code first counts the number of times a hit is made, and if it does, uses a query again to display the hits like online stores do. However, when I tested it, it only shows results from the vinyls table and not the products table. I've tried using UNION but because both tables have a different number of columns, it results in an error. I've used NULL to fill up the missing columns needed for union but it doesn't work too. Joins doesn't help either as the two tables do not have any similar column. What complicated it is the use of count(*) for the first query.
My SQL query using UNION and COUNT:
(SELECT COUNT(*) AS numrows
FROM vinyls
WHERE ( album_name LIKE :keyword
OR artist_name LIKE :keyword)
)
union
(SELECT COUNT(*) AS numrows
FROM products
WHERE name LIKE :keyword)
My php code for search field:
$stmt = $conn->prepare("(SELECT COUNT(*) AS numrows
FROM vinyls
WHERE ( album_name LIKE :keyword
OR artist_name LIKE :keyword)
)
union
(SELECT COUNT(*) AS numrows
FROM products
WHERE name LIKE :keyword)");
$stmt->execute(['keyword' => '%'.$_POST['keyword'].'%']);
$row = $stmt->fetch();
if($row['numrows'] < 1){
echo '<h1 class="page-header">No results found for <i>'.$_POST['keyword'].'</i></h1>';
}else{
echo '<h1 class="page-header">Search results for <i>'.$_POST['keyword'].'</i></h1>';
try{
$inc = 3;
$stmt = $conn->prepare("(SELECT *
FROM vinyls
WHERE ( album_name LIKE :keyword
OR artist_name LIKE :keyword)
)
union
(SELECT *
FROM products
WHERE name LIKE :keyword)");
$stmt->execute(['keyword' => '%'.$_POST['keyword'].'%']);
foreach ($stmt as $row) {...
I'm already stumped on how to search the 2 tables from only one search field and display the results from both tables and not only just one table. And it's a similar problem too when adding items to cart as they can be either from the two tables and I have to "join" the two tables again.
Where did I go wrong?
Edit:
Sample data
Vinyls table
+----+------------------+---------------------------+-----------+
| id | album_name | artist_name | genre |
+----+------------------+---------------------------+-----------+
| 11 | Ravel Bolero | Boston Symphony Orchestra | Classical |
| 12 | TV Calendar Show | Arthur Godfrey | Orchestra |
| 13 | Flip Phillips | The Phillips Quartet | Jazz |
| 14 | The Modern Idiom | Various artists | Jazz |
+----+------------------+---------------------------+-----------+
Products table
+----+-------------+------------------------------------------------------+
| id | category_id | name |
+----+-------------+------------------------------------------------------+
| 31 | 15 | Tonka/Diecast trucks and cars |
| 32 | 21 | Plate Number Georgia PQQ 1151 |
| 33 | 6 | Walt Disney Read Along Casette Tapes |
| 34 | 7 | Herbert Von Karajan |
| 35 | 8 | BANK IT! Board Game |
| 36 | 9 | Iraqi Most Wanted Playing Cards |
| 37 | 10 | STAR TREK ( 1991,'92,'93 ) Stamp Oasis Rubber Stamps |
| 38 | 11 | Batman and Friends Action Figure Toys (4" - 5") |
| 39 | 12 | Delta Dawn Porcelain Doll |
+----+-------------+------------------------------------------------------+
Expected result is similar to amazon's search bar, where you type a keyword and results show after you've entered. What I want in my site is that if I type orchestra in the search field, it will display Boston Symphony Orchestra's row. Or if I type cars, it will display the tonka row.
What I get is that it only shows the vinyls table and never the products table even if I type cars and there should have been a hit in the products table. Or I get an error because union is applicable only to tables with similar number of columns.

Answer 1

You have 2 problems in your code.
First, your count query should work and throw no error, but you only look at the first result row (the one of your vinyls). But your query returns two rows. (It will return one row with the numrows field for the first unioned query (vinyls) and one row with the numrows field for the second query (products) in your union.
You could wrap it into a SUM to only get one result row back:
$stmt = $conn->prepare("SELECT SUM(numrows) AS numrows FROM
(SELECT COUNT(*) AS numrows
FROM vinyls
WHERE ( album_name LIKE :keyword
OR artist_name LIKE :keyword)
)
union
(SELECT COUNT(*) AS numrows
FROM products
WHERE name LIKE :keyword)) AS sumQuery");
The second problem is the query, which loads your result and throws the exception because of the nonmatching column count. You have to define which columns of each of the two unioned queries should be returned, and they have to match on both. So f.e. do this:
$stmt = $conn->prepare("(SELECT id, album_name AS name, artist_name
FROM vinyls
WHERE ( album_name LIKE :keyword
OR artist_name LIKE :keyword)
)
union
(SELECT id, name, NULL AS artist_name
FROM products
WHERE name LIKE :keyword)");