Question

I have many queries, can I combine it into 1 to optimize?

1. SELECT COUNT(prod_id) FROM products WHERE inventory <= 5 AND cat_id = 1
2. SELECT COUNT(prod_id) FROM products WHERE inventory BETWEEN 5 AND 10 AND cat_id = 1
3. SELECT COUNT(prod_id) FROM products WHERE inventory > 10

Answer 1

I think this should work for you. It will return the 3 counts in a single SQL statement:

SELECT SUM(CASE WHEN inventory <= 5 AND cat_id = 1 THEN 1 ELSE 0 END) Q1Result,
   SUM(CASE WHEN inventory BETWEEN 5 AND 10 AND cat_id = 1 THEN 1 ELSE 0 END) Q2Result,
   SUM(CASE WHEN  inventory > 10 THEN 1 ELSE 0 END) Q3Result
FROM products 

And here is the SQL Fiddle.

Good luck.