web services - How to get and order rows from different tables with a limit and offset? -


i'm creating web services return list of chats , notifications. user can send input page number , number of items display per page, 2 types of objects can returned (from newest latest) , must displayed in same list.

i have 2 tables chat , notification

create table chat (   idchat serial not null,   idinterest integer not null,   idowner integer not null,   iduser integer not null,   creationdate,   editdate,   constraint pk_chat primary key (idchat) )  create table notification (   idnotification serial not null,   message character varying(255) not null,   creationdate date not null,   datefinvalidite date not null,   idcompte integer not null,   idtypenotification integer not null,   sender integer not null default 0,   constraint pk_notification primary key (idnotification) )

i create view groups chats , notifications, composed of id (idchat or idnotification), date (creationdate), , boolean ischat

but don't know if right solution.

problematic if have return 20 rows of ordered messages (notifications , chats) can either :

  • get 10 last notifications, 10 last chats, 9th chat might older 11th notification

  • check date of newest chat, if 20th newest notification older, notifications, otherwise ... don't know

  • get 20 newest notifications, 20 newest chats order them , send hem client heavy task server serves many requests @ same time.

select idchat id, creationdate, true ischat chat  union  select idnotification id, creationdate, false ischat notification  order creationdate desc limit 20

this version faster:

select *     (         (             select idchat id, creationdate, true ischat             chat             order creationdate desc             limit 20         )           union          (             select idnotification id, creationdate, false ischat             notification             order creationdate desc             limit 20         )      ) s  order creationdate desc limit 20

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