Get count of unmapped records when using a mapping table

I have 3 tables as such

Product

Vendor

Product Vendors

How would I go about finding the number of products that are not mapped to a specific vendor.

I tried:

SELECT
    COUNT(pr.id) AS product_count
FROM
    products pr
LEFT JOIN vendor_product_map vp ON
    pr.id = vp.product
LEFT JOIN vendors vv ON
    vp.vendor = vv.id
WHERE
    vv.id = 3 AND vp.vendor IS NULL

but that doesn’t seem right. Any help is appreciated

Edit:
For the above data, the expected results would be

Not Mapped Products

In short not mapped product count = total products – count of mapped products for a specific vendor, I’ll be specifying the vendor ID so the result set will have only 1 row. Hope that clarifies.

I got it to work using not exists and a subquery.

SELECT
    COUNT(pr.id) AS product_count
FROM
    products pr
WHERE NOT EXISTS(
    SELECT
        *
    FROM
        vendor_product_map vp
    WHERE
        vp.product = pr.id AND vp.vendor = 3
)

If you know for sure that a product will always be properly linked to a vendor, you could use an INNER JOIN, and simply filter out results where vender_id = 3.

SELECT COUNT(*) AS product_count
FROM products AS pr
    INNER JOIN vendor_product_map AS vp ON pr.id = vp.product
WHERE vp.vendor <> 3

If vendor might ever be NULL, and you want those results as well, you’d want to stick with a LEFT JOIN, like this…

SELECT COUNT(*) AS product_count
FROM products AS pr
    LEFT JOIN vendor_product_map AS vp ON pr.id = vp.product
WHERE vp.vendor <> 3 OR vp.vendor IS NULL