Mysql order by with grouping - mysql

Question

Hello everyone today i got in to a problem..
first thing i have a two table each table i have "product_seq_id" column and i joined table using the same "product_seq_id"
in the second table there are multiple rows for "product_seq_id" i want only one with below condition
table2.date_start not be null
table2.date_start is equal to '0000-00-00' or table2.date_start <= CURDATE()
table2.date_end is equal to '0000-00-00' or table2.date_start >= CURDATE()
get highest table2.priority if 2 or more rows match on the same day
I have already did some work.. but the problem is in that it's not taking highest priority number while ordering the column with grouped
//My Query
SELECT
psp . *, pcp . *
FROM
sk_product_category_path pcp
left join
sk_product_special_price psp ON (psp.product_seq_id = pcp.product_seq_id)
where
pcp.category_seq_id = 146
AND psp.product_seq_id IS NOT NULL
AND CASE
WHEN
psp.date_start IS NOT NULL
THEN
(psp.date_start = '0000-00-00'
OR psp.date_start <= CURDATE())
AND (psp.date_end = '0000-00-00'
OR psp.date_end >= CURDATE())
ELSE 1 = 1
END
group by psp.product_seq_id
order by psp.priority desc
Result Came for above code:
# product_special_price_seq_id, product_special_price, date_start, date_end, priority, product_seq_id, product_category_path_seq_id, product_seq_id, category_seq_id
2309 123123 0000-00-00 0000-00-00 0 3196 1 3196 146
2307 12313 0000-00-00 0000-00-00 0 3197 3 3197 146
Result I wanted:
# product_special_price_seq_id, product_special_price, date_start, date_end, priority, product_seq_id, product_category_path_seq_id, product_seq_id, category_seq_id
2309 12200 0000-00-00 0000-00-00 1 3196 2 3196 146
2307 12313 0000-00-00 0000-00-00 0 3197 3 3197 146
// Table Data
CREATE TABLE IF NOT EXISTS `sk_product_category_path` (
`product_category_path_seq_id` int(11) NOT NULL AUTO_INCREMENT,
`product_seq_id` int(11) NOT NULL,
`category_seq_id` int(11) NOT NULL,
PRIMARY KEY (`product_category_path_seq_id`),
UNIQUE KEY `product_seq_id` (`product_seq_id`,`category_seq_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;
INSERT INTO `sk_product_category_path` (`product_category_path_seq_id`, `product_seq_id`, `category_seq_id`) VALUES
(1, 3196, 146),
(2, 3197, 146),
(3, 3198, 146);
CREATE TABLE IF NOT EXISTS `sk_product_special_price` (
`product_special_price_seq_id` int(11) NOT NULL AUTO_INCREMENT,
`product_special_price` bigint(20) DEFAULT NULL,
`date_start` date DEFAULT NULL,
`date_end` date DEFAULT NULL,
`priority` int(11) DEFAULT NULL,
`product_seq_id` int(11) NOT NULL,
PRIMARY KEY (`product_special_price_seq_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;
INSERT INTO `sk_product_special_price` (`product_special_price_seq_id`, `product_special_price`, `date_start`, `date_end`, `priority`, `product_seq_id`) VALUES
(1, 12313, '0000-00-00', '0000-00-00', 0, 3197),
(2, 12200, '2014-02-11', '2014-02-11', 1, 3197),
(3, 123123, '0000-00-00', '0000-00-00', 0, 3196);

Answer 1

During GROUP BY in MySQL, it picks first matching row for each group unless you are using an aggregate function. The first matching need not be always row with min(id) .
The possible query should be something like :
SELECT t.*
from table_name t
inner join (
select min(id) as id
from table_name t
group by col) as s
on s.id = t.id

Answer 2

Please find the below query.. let me know is this is your requirement?
SELECT *
FROM sk_product_special_price pspo
WHERE pspo.priority IN(SELECT MAX(psp.priority)
FROM sk_product_special_price psp
JOIN sk_product_category_path pcp
ON(pcp.product_seq_id=psp.product_seq_id)
WHERE psp.date_start IS NOT NULL
AND psp.date_start BETWEEN '0000-00-00' AND CURDATE()
AND (psp.date_end>=CURDATE() OR psp.date_end='0000-00-00')
AND pcp.product_seq_id=pspo.product_seq_id);
I have updated the end date "'2014-02-11" to "2014-02-12" for my code to fetch end date >=today's date.
this query will return the table2 details i.e table sk_product_special_price for each all the product based on the priyority values.
the output will be
product_special_price_seq_id, product_special_price, date_start, date_end, priority, product_seq_id
2, 12200, '2014-02-11', '2014-02-12', 1, 3197
3, 123123, '0000-00-00', '0000-00-00', 0, 3196