Question

I’ve always been confused on how to combine multiple MySQL queries into one. I’ve been pulling my hair out trying to do the following. First, I do a query to get a result of each vendor and how many products they have:

SELECT vendor_name, COUNT(vendor_name) AS cnt FROM products GROUP BY vendor_name

Next, as I only want those vendors who have 10 or more products, I do the following PHP IF statement. I don’t know how to incorporate this in the above SELECT, so I do it via PHP. I know, it’s not the best, but when you don’t know the best way, you need to do it some way:

if ($database_row['cnt']>=10) {

Within this IF statement, I then do a query on each of the vendors that have 10 or more products:

SELECT id FROM products WHERE vendor_name="'.$database_row['vendor_name'].'"

Which gives me the id’s of each product for vendors that have at least 10 products. I know, it’s sloppy, but it generates the correct results. The issue is that I need all of this to be in one query and for the life of me I can’t figure it out. Both of these queries are in the same database, and it doesn’t seem to be that complex of a request, which is really just “show me the products of those vendors who have 10 or more products”.

Can the above be combined into one query? The current full PHP/MySQL code is as follows:

$database_result = @mysql_query('SELECT vendor_name, COUNT(vendor_name) AS cnt FROM products GROUP BY vendor_name',$database_conn);
while($database_row = @mysql_fetch_array($database_result)) {
  if ($database_row['cnt']>=10) {
    $database_result2 = @mysql_query('SELECT id FROM products WHERE vendor_name="'.$database_row['vendor_name'].'"',$database_conn);
    // Process results
  }
}

Thanks in advance!

---

Here’s the full single query that now works exactly as I wanted. Maybe there’s a clever way optimize the query, but it works and seems fast enough. Thanks to all!

SELECT
  p3.*
FROM
(
  SELECT
    p1.id,
    p1.department,
    p1.end_date,
    p1.quantity_sold,
    p2.vendor_name
  FROM
    products p1
  INNER JOIN
  (
    SELECT
      vendor_name
    FROM
      products
    GROUP BY
      vendor_name
    HAVING
      COUNT(*) >= 10
  ) p2
  ON
    p1.vendor_name = p2.vendor_name
  AND
    p1.sold_out = 0
  AND
    p1.end_date > NOW()
  ORDER BY
    p1.end_date DESC
) AS p3
GROUP BY
  p3.vendor_name
ORDER BY
  p3.quantity_sold DESC

Answer 1

Try this

SELECT 
    p1.id,
    p1.vendor_name 
FROM 
    products p1 
    INNER JOIN
    (
       SELECT 
          vendor_name,
          COUNT(vendor_name) as productCount 
       FROM 
          products 
       GROUP BY 
          vendor_name
       HAVING
          productCount >= 10
    ) p2
    ON p1.vendor_name=p2.vendor_name