How to fetch the started on date when a price is changed (price is not incremental)
https://dba.stackexchange.com/questions/193188
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I am trying to build a single query that will allow me to fetch the first saved_on date from when a price was assigned.
The tricky part is this data needs to only be within the most recent changes for that price. Meaning, if the price were $5 then changed the $6 and then changes back to $5, I need to only query the $5 change date after it was $6 to get the correct price started on date. Since the price was $6 between the $5, I want to ignore any $5 before it was changed to $6.
I am just trying to make a report of when an item's price was last updated to the latest price. Due to some other constraints, I need control over the price because there are some cases where the latest price will be the previous price. To prevent any issues, I want to add the price to the conditional.
What I am trying to do is very similar to this request but slightly different. I tried to use the updated example as this seems to be closest to what I am trying to do but have had no success.
The query needs to work by selecting a custno, item, and price. The price is assumed to be the current price but can be changed to be an earlier price.
I have tried to do something like:
SELECT
saved_on
FROM customer_items
WHERE custno = '{$custno}'
AND item = '{$item}'
AND price = {$price}
AND saved_on > (
SELECT
saved_on
FROM customer_items
WHERE custno = '{$custno}'
AND item = '{$item}'
AND price <> {$price}
ORDER BY week_of DESC
LIMIT 1
)
ORDER BY week_of ASC
LIMIT 1
This works on some but not all the items.
Tests:
I am a bit stuck. Hopefully someone here can push me in the correct direction.
DB Schema and Data:
-- Create Table
CREATE TABLE IF NOT EXISTS `customer_items` (
`cid` bigint(20) AUTO_INCREMENT NOT NULL,
`item` varchar(15) NOT NULL,
`custno` varchar(6) NOT NULL,
`week_of` date NOT NULL,
`price` double(12,4) NOT NULL,
`saved_on` datetime NOT NULL,
PRIMARY KEY (`cid`),
UNIQUE KEY `custno_item_weekof` (`custno`,`item`,`week_of`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
-- Add Data for test 1 (ALLPR - OYDI2505B)
INSERT INTO `customer_items` (`cid`, `item`, `custno`, `week_of`, `price`, `saved_on`) VALUES
(NULL, 'OYDI2505B', 'ALLPR', '2017-12-11', 4.25, '2017-12-07 16:57:50'), -- Expect this for current price start date
(NULL, 'OYDI2505B', 'ALLPR', '2017-10-09', 3.25, '2017-10-05 09:26:48'),
(NULL, 'OYDI2505B', 'ALLPR', '2017-02-27', 3.00, '2017-02-22 14:45:33'),
(NULL, 'OYDI2505B', 'ALLPR', '2015-06-08', 3.00, '2015-06-04 15:55:02'), -- Expect this for when I select the 3.00 price for the start date
(NULL, 'OYDI2505B', 'ALLPR', '2015-06-01', 3.75, '2015-05-28 16:03:02'),
(NULL, 'OYDI2505B', 'ALLPR', '2015-03-30', 3.25, '2015-03-26 14:26:18'),
(NULL, 'OYDI2505B', 'ALLPR', '2015-02-09', 3.25, '2015-02-02 16:17:48'),
(NULL, 'OYDI2505B', 'ALLPR', '2015-01-05', 2.95, '2014-12-30 10:41:33'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-12-29', 3.00, '2014-12-23 11:30:33'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-11-10', 2.95, '2014-11-03 15:29:29'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-10-20', 2.95, '2014-10-16 18:13:58'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-10-13', 3.00, '2014-10-08 10:42:54'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-09-22', 2.95, '2014-09-19 17:32:46'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-09-15', 2.95, '2014-09-11 17:29:53'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-09-08', 2.95, '2014-09-04 17:58:39'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-09-01', 2.95, '2014-08-29 18:00:35'),
(NULL, 'OYDI2505B', 'ALLPR', '2014-07-07', 3.00, '2014-08-13 21:09:11');
-- Add Data for test 2 (JPFS - LT3WCS )
INSERT INTO `customer_items` (`cid`, `item`, `custno`, `week_of`, `price`, `saved_on`) VALUES
(NULL, 'LT3WCS', 'JPFS', '2017-10-09', 3.25, '2017-10-05 09:26:48'), -- Expect this for current price start date
(NULL, 'LT3WCS', 'JPFS', '2017-02-27', 4.00, '2017-02-22 14:45:33'),
(NULL, 'LT3WCS', 'JPFS', '2015-06-08', 4.00, '2015-06-04 15:55:02'),
(NULL, 'LT3WCS', 'JPFS', '2015-06-01', 3.75, '2015-05-28 16:03:02'),
(NULL, 'LT3WCS', 'JPFS', '2015-03-30', 3.25, '2015-03-26 14:26:18'),
(NULL, 'LT3WCS', 'JPFS', '2015-02-09', 3.25, '2015-02-02 16:17:48'),
(NULL, 'LT3WCS', 'JPFS', '2015-01-05', 2.95, '2014-12-30 10:41:33'),
(NULL, 'LT3WCS', 'JPFS', '2014-12-29', 2.95, '2014-12-23 11:30:33'),
(NULL, 'LT3WCS', 'JPFS', '2014-11-10', 2.95, '2014-11-03 15:29:29'),
(NULL, 'LT3WCS', 'JPFS', '2014-10-20', 2.95, '2014-10-16 18:13:58'),
(NULL, 'LT3WCS', 'JPFS', '2014-10-13', 2.95, '2014-10-08 10:42:54'), -- Expect this for when I select the $2.95 price for the start date
(NULL, 'LT3WCS', 'JPFS', '2014-09-22', 4.00, '2014-09-19 17:32:46'),
(NULL, 'LT3WCS', 'JPFS', '2014-09-15', 2.95, '2014-09-11 17:29:53'),
(NULL, 'LT3WCS', 'JPFS', '2014-09-08', 2.95, '2014-09-04 17:58:39'),
(NULL, 'LT3WCS', 'JPFS', '2014-09-01', 2.95, '2014-08-29 18:00:35'),
(NULL, 'LT3WCS', 'JPFS', '2014-07-07', 2.63, '2014-08-13 21:09:11');
-- Add Data for test 3 (99ST - FAMIX1212OZCS)
INSERT INTO `customer_items` (`cid`, `item`, `custno`, `week_of`, `price`, `saved_on`) VALUES
(NULL, 'FAMIX1212OZCS', '99ST', '2017-12-11', 6.60, '2017-12-07 16:11:46'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-11-27', 6.60, '2017-11-22 17:04:13'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-11-20', 6.60, '2017-11-16 19:09:14'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-11-13', 6.60, '2017-11-09 19:34:49'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-11-06', 6.60, '2017-11-02 19:10:20'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-10-30', 6.60, '2017-10-26 18:13:32'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-10-23', 6.60, '2017-10-19 18:30:44'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-08-07', 6.60, '2017-08-03 16:46:47'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-07-10', 6.60, '2017-07-07 16:19:37'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-06-26', 6.60, '2017-06-22 16:12:35'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-04-03', 6.60, '2017-03-30 20:29:50'),
(NULL, 'FAMIX1212OZCS', '99ST', '2017-03-13', 6.60, '2017-03-09 18:18:26'), -- Expect this for current price start date
(NULL, 'FAMIX1212OZCS', '99ST', '2017-02-27', 7.20, '2017-02-23 16:57:30'), -- Expect this for when I select the $7.20 price for the start date
(NULL, 'FAMIX1212OZCS', '99ST', '2017-02-13', 6.60, '2017-02-09 17:08:33'),
(NULL, 'FAMIX1212OZCS', '99ST', '2016-12-12', 6.60, '2016-12-08 19:02:19'),
(NULL, 'FAMIX1212OZCS', '99ST', '2016-12-05', 6.60, '2016-12-01 16:48:14'),
(NULL, 'FAMIX1212OZCS', '99ST', '2016-11-14', 6.60, '2016-11-10 15:47:55'),
(NULL, 'FAMIX1212OZCS', '99ST', '2016-10-10', 6.60, '2016-10-04 12:22:09');
-- Add Data for test 4 (KBSF - CAST1255B )
INSERT INTO `customer_items` (`cid`, `item`, `custno`, `week_of`, `price`, `saved_on`) VALUES
(NULL, 'CAST1255B', 'KBSF', '2017-12-11', 6.60, '2017-12-07 16:11:46'),
(NULL, 'CAST1255B', 'KBSF', '2017-02-13', 6.60, '2017-02-09 17:08:33'),
(NULL, 'CAST1255B', 'KBSF', '2016-12-12', 6.60, '2016-12-08 19:02:19'),
(NULL, 'CAST1255B', 'KBSF', '2016-12-05', 6.60, '2016-12-01 16:48:14'),
(NULL, 'CAST1255B', 'KBSF', '2016-11-14', 6.60, '2016-11-10 15:47:55'),
(NULL, 'CAST1255B', 'KBSF', '2016-10-10', 6.60, '2016-10-04 12:22:09'); -- Expect this for current price start date
Solution
Maybe the following query will give you a starting point for writing your own ... Principle: select 4 columns from your customer_items table (derived table dt). Then, use 2 user-defined variables that will allow us to number the prices. At a particular date, a particular price was recorded for the first time. Its "number" will be: 1. If the same price is used again, its "number" will be 2 etc. Whenever a new/different price has been recorded, the numbering is interrupted (and the numbers start at 1 again). Example:
select
dt.custno
, dt.item
, dt.saved_on
, @number_ := if( @price_ = dt.price, @number_, 0 ) + 1 as occp -- occurence of current price
, @price_ := dt.price price
from
(
select
custno
, saved_on
, price
, item
from customer_items
order by custno, saved_on
) dt
-- JPFS | LT3WCS section of dt:
...
| JPFS | LT3WCS | 2014-08-13 21:09:11 | 1 | 2.6300 |
| JPFS | LT3WCS | 2014-08-29 18:00:35 | 1 | 2.9500 |
| JPFS | LT3WCS | 2014-09-04 17:58:39 | 2 | 2.9500 |
| JPFS | LT3WCS | 2014-09-11 17:29:53 | 3 | 2.9500 |
| JPFS | LT3WCS | 2014-09-19 17:32:46 | 1 | 4.0000 |
| JPFS | LT3WCS | 2014-10-08 10:42:54 | 1 | 2.9500 |
| JPFS | LT3WCS | 2014-10-16 18:13:58 | 2 | 2.9500 |
| JPFS | LT3WCS | 2014-11-03 15:29:29 | 3 | 2.9500 |
| JPFS | LT3WCS | 2014-12-23 11:30:33 | 4 | 2.9500 |
| JPFS | LT3WCS | 2014-12-30 10:41:33 | 5 | 2.9500 |
| JPFS | LT3WCS | 2015-02-02 16:17:48 | 1 | 3.2500 |
| JPFS | LT3WCS | 2015-03-26 14:26:18 | 2 | 3.2500 |
| JPFS | LT3WCS | 2015-05-28 16:03:02 | 1 | 3.7500 |
| JPFS | LT3WCS | 2015-06-04 15:55:02 | 1 | 4.0000 |
| JPFS | LT3WCS | 2017-02-22 14:45:33 | 2 | 4.0000 |
| JPFS | LT3WCS | 2017-10-05 09:26:48 | 1 | 3.2500 |
...
You are only interested in the most recent change of a particular price. Its "number" will be: 1. The most recent price labelled "1" can be found with MAX( saved_on ). Thus, we add another SELECT and some conditions eg
select
max( saved_on )
from
(
select
dt.custno
, dt.item
, dt.saved_on
, @number_ := if( @price_ = dt.price, @running, 0 ) + 1 as occp -- occurence of current price
, @price_ := dt.price price
from
(
select
custno
, saved_on
, price
, item
from customer_items
order by custno, saved_on
) dt
) dt2
where occp = 1
and custno = 'JPFS'
and item = 'LT3WCS'
and price = 2.95
;
-- result
+---------------------+
| max( saved_on ) |
+---------------------+
| 2014-10-08 10:42:54 |
+---------------------+
1 row in set (0.00 sec)
For the query that did not give you a result ( custno = 'ALLPR' and item = 'OYDI2505B' and price = 3.25 ) , we get:
+---------------------+
| max( saved_on ) |
+---------------------+
| 2017-10-05 09:26:48 |
+---------------------+
1 row in set (0.00 sec)
Tested with MySQL 5.7 and 5.6, using your test data. SQL Fiddle here.
