Laravel中的MySQL子查询，如何联接查询并将第二查询的结果作为新列添加到第一查询？

Question

I have two tables:

- PRODUCTS (having: ID, NAME, PRICE)
- LIKES (having: ID, PRODID, NAME)

I would like to query the first table while counting (and returning as a new column) in a sub query all the likes the product has. How could I combine the following queries?

$products = DB::table('PRODUCTS')
                  ->get();

$likes = DB::table('LIKES')
                  ->select(DB::raw('count(*) as total'))
                  ->where('PRODID', '=', 'product id from first table')
                  ->get();

How could I achieve this using Laravel queries? Thanks!

Answer 1

Not the answer you specifically asked for but as an alternative, this would be extremely easy to handle with Eloquent.

$products = Product::with('likes');
foreach ($products as $product) {
    echo 'Number of likes: '.$product->likes->count();
}

Answer 2

Use a join with a group by clause, rather than a subquery. This way you can get the counts for all products in one go, you do not have to query the counts one by one. The sql looks like as follows:

select p.id, p.name, p.price, count(l.id) as likecount
from products p
left join likes l on p.id=l.prodid
group by p.id, p.name, p.price

Answer 3

Try like this

$likes = DB::table('LIKES')
      ->join('PRODUCTS', 'LIKES.PRODID', '=', 'PRODUCTS.id') 
      ->select('LIKES.*') 
      ->where('PRODUCTS.id', '=', 3)      
      ->get();
$total_like = count($likes);