mysql counting rows with loop

Question

I have the following table:

+-------------+--------------+ 
| product     | purchased    |
+-------------+--------------+ 
| Hammer      |   |
|         


        

Answer 1

Better normalization would speed up this query tremendously, but here's an example to work from:

First, you need to start with your base query, the one that will drive the results. In this case, it's a list of all the products in your table:

SELECT DISTINCT product
FROM   productWarranty

The above query creates a sort of "temp" table that we can base our queries on. If you have a separate, normalized product table then that would be much better.

The rest of the columns can simply be subqueries driven by your base table:

Total count:

SELECT COUNT(*)
FROM   productWarranty
WHERE  product = 'Hammer'

Total valid warranties:

SELECT COUNT(*)
FROM   productWarranty
WHERE  product = 'Hammer'
   AND purchased >= 

Total expired warranties:

SELECT COUNT(*)
FROM   productWarranty
WHERE  product = 'Hammer'
   AND purchased < 

Last purchase date:

SELECT MAX( purchased )
FROM   productWarranty
WHERE  product = 'Hammer'

Now to combine all of these into a single query:

SELECT  Base.product
    ,   (
            SELECT COUNT(*)
            FROM   productWarranty
            WHERE  product = Base.product
        ) AS TotalCount
    ,   (
            SELECT COUNT(*)
            FROM   productWarranty
            WHERE  product = Base.product
               AND date_add(from_unixtime(purchased), INTERVAL 5 YEAR) >= CURDATE()
        ) AS ValidWarrantyCount
    ,   (    
            SELECT COUNT(*)
            FROM   productWarranty
            WHERE  product = Base.product
               AND date_add(from_unixtime(purchased), INTERVAL 5 YEAR) < CURDATE()
        ) AS ExpiredWarrantyCount
    ,   (
            SELECT MAX( purchased )
            FROM   productWarranty
            WHERE  product = Base.product
        ) AS LastPurchased
FROM    (
            SELECT DISTINCT product
            FROM   productWarranty
        ) AS Base