mysql - Query to delete old records, with an exception -


lets have table keeps history of prices, example:

 _______________________________________________________ |make  | model |  year  |  price  |    date_of_record   | |-------------------------------------------------------- |mazda |   6   |  2008  | 10,000  | 2013-05-13 00:00:00 | |mazda |   6   |  2008  | 11,000  | 2012-05-13 00:00:00 | |mazda |   6   |  2008  | 12,000  | 2011-05-13 00:00:00 | |mazda |   6   |  2008  | 11,750  | 2010-05-13 00:00:00 | |honda | civic |  2000  | 3,000   | 2011-05-13 00:00:00 | |honda | civic |  2000  | 4,000   | 2010-05-13 00:00:00 | |honda | civic |  2000  | 5,000   | 2009-05-13 00:00:00 | |honda | civic |  2000  | 5,050   | 2008-05-13 00:00:00 | |acura |   tl  |  2009  | 21,000  | 2010-05-13 00:00:00 | |--------------------------------------------------------

i want delete entries more 2 years old unless latest entry more 2 years old. hard put words, want end this:

 _______________________________________________________ |make  | model |  year  |  price  |    date_of_record   | |-------------------------------------------------------- |mazda |   6   |  2008  | 10,000  | 2013-05-13 00:00:00 | |mazda |   6   |  2008  | 11,000  | 2012-05-13 00:00:00 | |honda | civic |  2000  | 3,000   | 2011-05-13 00:00:00 | |acura |   tl  |  2009  | 21,000  | 2010-05-13 00:00:00 | |--------------------------------------------------------

so query delete entries more 2 years old mazda, , entries more 2 years old honda , acura, exception of latest.

entries inserted table when price changes, if price hasn't changed in 5 years entry 5 years old, not mean data not accurate.

first, lets list of car, make, model, year , respective latest "date of record". so, have 2007 vehicle , 2008 of same make/model each latest date entry of 2011-01-01. want keep vehicle entry both 2007 , 2008 models however, example showed old dates want keep retained data honda civic , acural tl respectively.

run this, confirm results

select        c.`make`,       c.`model`,       c.`year`,       max( c.date_of_record ) latestrecorddate           yourcarpricetable c    group       c.`make`,       c.`model`,       c.`year`    having       max( c.date_of_record ) < date_add(curdate(),interval -2 year)

now, use basis delete current table via left join on same make, model , year. 2 conditions allow delete.
1) there no match found in "keepthese" subquery , latest date of record more 2 years old...

2) there match found in "keepthese" subquery , date older recent qualified (too old) result set of keepthese.

per data example, "keepthese" result set should include

make   model   year   latestrecorddate honda  civic   2000   2011-05-13 00:00:00 acura  tl      2009   2010-05-13 00:00:00

so, mazda 6 delete 2 entries 2010 , 2011 date entries since make/model/year not included in list (via test null).

your honda civic delete entries older it's latest "keepthese" value of 2011-05-13, , delete 2008, 2009 , 2010 entries.

your acura tl not have older it's single entry, left alone.

delete ypt.*    yourcarpricetable ypt       left join ( select                          c.`make`,                         c.`model`,                         c.`year`,                         max( c.date_of_record ) latestrecorddate                                               yourcarpricetable c                      group                         c.`make`,                         c.`model`,                         c.`year`                      having                         max( c.date_of_record ) < date_add(curdate(),interval -2 year) ) keepthese          on ypt.`make` = keepthese.`make`          , ypt.`model` = keepthese.`model`          , ypt.`year` = keepthese.`year`          (     keepthese.`make` null         , ypt.date_of_record < date_add(curdate(),interval -2 year))       or       (      ypt.`make` = keepthese.`make`          , ypt.`model` = keepthese.`model`          , ypt.`year` = keepthese.`year`          , ypt.date_of_record < keepthese.latestrecorddate )

the subquery processed once front, left-joined delete version of car/price table.


Comments

Post a Comment

Popular posts from this blog

jquery - How can I dynamically add a browser tab? -

since using iframes house external pages are, accounts "not preferred method" , disallowed sites (flickr, one), want dynamically generate browser tabs. e.g., when user submits form, want dynamically generate tab on browser in response submitted. e.g., might want add new tab url like: http://www.bigsurgarrapata.com/contact how in jquery? you want form target attribute action attribute. http://www.w3schools.com/tags/att_form_target.asp browsers have ultimate control on result of target attribute open new tab value of _blank. <form action="contact_submit.php" target="_blank" method="post">
Read more

node.js - Getting the socket id,user id pair of a logged in user(s) -

i have web application done using node js , in it,i have authentication system requires users log in before can access pages. have 2 pages,the homepage , updates page. from read docs,a new socket id issued when user opens tab in browser. me being admin,i know socket id of logged in user , more so,the socket id,logged in user id pair logged in users. what method can use socket id,logged in user id pair make sure broadcast realtime info users online?.
Read more

keyboard - C++ GetAsyncKeyState alternative -

i using windows.h library's getasynckeystate function define key pushed on keyboard . here program returns int value of pushed key example. #include <iostream> #include <windows.h> using namespace std; int main (){ char i; for(i=8;i<190;i++){ if(getasynckeystate(i)== -32767){ cout<<int (i)<<endl; } } return 0; } but trying make opengl simple game , function appeared slow . there function not need cycle 180 times , if statement . thanks you're trying make opengl game, you're going use glfw. if that's case can away using glfwgetkey() such: if (glfwgetkey(glfw_key_up) == glfw_press) {...} if (glfwgetkey(glfw_key_down) == glfw_press) {...} that method nicely explained in tutorial 6 opengl-tutorial.org . should start first tutorial of beginners tutorials , later intermediate tutorials . if you're going make win32 window can listen wm_keydown or wm_keyup messages , virtua
Read more