mysql getting max min values across multiple tables - php

Question

I want to get a price range for some products from two tables.
Table1 (products):
pid | products_name | products_model
1 | Product 1.....| model 1
2 | Product 2.....| model 2
Table2 (products_prices):
pid | nerchant_id | price | sale_price | sale_start_date | sale_expire_date
1 | RVTBV | 11.90 | 0 | NULL | NULL
1 | QNUNU | 11.90 | 9.90 | 2013-05-01 | 2013-12-31
1 | YOLOR | 12.90 | 10.90 | 2013-04-01 | 2013-12-31
2 | RVTBV | 20.90 | 0 | NULL | NULL
2 | QNUNU | 29.90 | 25.90 | 2013-04-01 | 2013-12-31
2 | YOLOR | 29.90 | 0 | NULL | NULL
How do I get a result with price range to look like this:
pid | products_name | products_model | min_price | max_price
1 | Product 1.... | model 1 ...... | 10.90 ... | 12.90
2 | Product 2.... | model 2 ...... | 20.90 ... | 29.90
I am using a main query to get products data from table1 then a loop with php foreach product to get the min max values depending on sale start and expiry dates.
It does the work but I don't like subqueries with php. I prefer one MySQL query for performance reasons.
Thanks for helping.
Until now the following statement the best
SELECT p.pid,
p.manufacturers_id,
p.products_image,
p.products_name,
(select min(if(CURRENT_DATE BETWEEN pp.sale_start_date AND pp.sale_expire_date and pp.sale_price>'0', pp.sale_price, pp.price)) from products_prices pp where p.pid = pid) as min_price,
(select max(if(CURRENT_DATE BETWEEN pp.sale_start_date AND pp.sale_expire_date and pp.products_sale_price>'0', pp.sale_price, pp.price)) from products_prices pp where p.pid = pp.pid) as max_price
FROM products p
WHERE p.products_status = '1'
AND p.categories_id = '1'
ORDER BY min_price ASC LIMIT 0, 100
is it possible to optimize it a little bit?
Resumé:
sometimes is the solution so simple that i don´t see it;)
ok the project is an price comparison plattform. Products will be updated hourly or something like that, but not all prices will change. So let´s say 10% will be updated.
But the data must be retrieverd with each visit of the website.
In this case it will be more reads than writes (80-20).
I can add two extra columns to the products table (min_price and max_price) that i update only once if price_data changes.
on one Hand the update will be a little bit more complicated but that´s not a drama. On the other hand the data will be retrieved very fast.
I have testet 3 options based on 15000 products to retrieve 100 rows:
worst: the group by approch (over 1 sec)
good: the approach of arheops (0,12 sec)
best: update once with two extra colums (0,07 sec)
I go with the third option.
thanks for your help anyway!

Answer 1

That depend of you query.
If you query only some values from product, this will be optimal:
select pid,products_name,products_model,
(select min(price) from price where price.pid=product.pid) as min_price,
(select max(price) from price where price.pid=product.pid) as max_price
from product where some_filter_here;
If you need got FULL table, this one is best:
select a.pid,products_name,products_model,min_price,max_price
from product as a
left join (
select pid,min(price) as min_price, max(price) as max_price
from price group by pid
) as b on b.pid=a.pid

Answer 2

SELECT products.*,
MIN(IF(CURRENT_DATE BETWEEN sale_start_date AND sale_expire_date, sale_price, price)) min_price,
MAX(price) max_price
FROM products JOIN products_prices USING (pid)
GROUP BY pid
See it on sqlfiddle.

Answer 3

The below should work for your requirements.
Update:
The first query now also considers the start/end date for the sale price
SELECT
p.pid,
p.products_name,
p.products_model,
pp.price as min_price,
pp.sale_price as max_price
FROM
products p
JOIN products_prices pp ON ( p.pid = pp.pid )
LEFT JOIN products_prices pp2 ON ( pp2.pid = pp.pid AND pp2.price > pp.price AND pp.sale_start_date BETWEEN pp2.sale_start_date AND pp2.sale_expire_date )
WHERE
pp2.pid IS NULL AND NOW() BETWEEN pp.sale_start_date and pp.sale_expire_date
The below one, gets the max, min of the prices avaliable for a product
SELECT
p.pid,
p.products_name,
p.products_model,
MIN( LEAST( pp.price, pp.sale_price) ) as min_price,
MAX( GREATEST( pp.price, pp.sale_price) ) as max_price
FROM
products p
JOIN products_prices pp ON ( p.pid = pp.pid )
WHERE
pp.sale_price <> 0
GROUP BY
p.pid
SQLFIDDLE

Answer 4

I think you're actually after this. I've amended sale_price to NULL in the event that there is no sale which is just as it should be if you're going to insist on including sale information in the products_prices table...
DROP TABLE IF EXISTS products;
CREATE TABLE products
(pid INT NOT NULL AUTO_INCREMENT PRIMARY KEY
,products_name VARCHAR(12) NOT NULL
,products_model VARCHAR(12) NOT NULL
);
INSERT INTO products VALUES
(1 ,'Product 1','model 1'),
(2 ,'Product 2','model 2');
DROP TABLE IF EXISTS products_prices;
CREATE TABLE products_prices
(pid INT NOT NULL
,merchant_id CHAR(5) NOT NULL
,price DECIMAL(5,2)NOT NULL
,sale_price DECIMAL(5,2) NULL
,sale_start_date DATE
,sale_expire_date DATE
,PRIMARY KEY(pid,merchant_id)
);
INSERT INTO products_prices VALUES
(1,'RVTBV',11.90,NULL,NULL,NULL),
(1,'QNUNU',11.90,9.90,'2013-05-01','2013-12-31'),
(1,'YOLOR',12.90,10.90,'2013-04-01','2013-12-31'),
(2,'RVTBV',20.90,NULL,NULL,NULL),
(2,'QNUNU',29.90,25.90,'2013-04-01','2013-12-31'),
(2,'YOLOR',29.90,NULL,NULL,NULL);
SELECT p.*
, MIN(CASE WHEN CURDATE() BETWEEN sale_start_date AND sale_expire_date THEN pp.sale_price ELSE pp.price END) min_price
, MAX(CASE WHEN CURDATE() BETWEEN sale_start_date AND sale_expire_date THEN pp.sale_price ELSE pp.price END) max_price
FROM products p
JOIN products_prices pp
ON pp.pid = p.pid
GROUP
BY p.pid;
+-----+---------------+----------------+-----------+-----------+
| pid | products_name | products_model | min_price | max_price |
+-----+---------------+----------------+-----------+-----------+
| 1 | Product 1 | model 1 | 10.90 | 11.90 |
| 2 | Product 2 | model 2 | 20.90 | 29.90 |
+-----+---------------+----------------+-----------+-----------+