Some sample data showing the relationships between the tables would be great. There are a number of ways of structuring this type of query which has different aggregates hanging off key values, which one is best for you will depend on the data. Here's one way which is at least easy to understand, if not the fastest:
;WITH CTE_ProductReviews AS (
SELECT p2p.path_id, p2p.prod_id, o.ReviewCount
FROM p2p
INNER JOIN (products) p ON p.prod_id = p2p.prod_id AND p.[status] = 0
LEFT JOIN (SELECT product_id, COUNT(*) AS ReviewCount
FROM Reviews
WHERE [status] = 0
GROUP BY product_id) o ON o.product_id = p.product_id
WHERE p2p.[status] = 0)
SELECT c.name,
d1.ProductCount AS 'Total products',
d1.ReviewCount AS 'Total Reviews',
d2.ProductCount AS 'Prod. With 1 Review'
FROM c
INNER JOIN pv ON pv.cat_id = c.cat_id AND pv.step = 1
INNER JOIN (SELECT path_id,
COUNT(*) AS ProductCount,
SUM(ReviewCount) AS ReviewCount
FROM CTE_ProductReviews
GROUP BY path_id) d1 ON d1.path_id = pv.path_id
INNER JOIN (SELECT path_id,
COUNT(*) AS ProductCount
FROM CTE_ProductReviews
WHERE ReviewCount = 1
GROUP BY path_id) d2 ON d2.path_id = pv.path_id
WHERE c.[status] = 0
ORDER BY c.name
Cheers
ChrisM
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden