mysql - Get biggest value of group after join -


i have 2 tables in db:

conversation:

conversationid | persone | perstwo | timestamp 1              |    1    |  3      | 1431680294000 2              |    3    |  8      | 1431680407000

message:

messageid | conversationid | senderid | receiverid | message | timestamp     |  seen 1           1                1          3            xyz!      1431680294000    0 2           2                3          8            hi x!     1431680405000    0 3           2                3          8            allt bra? 1431680407000    0

now want find latest message of each conversation.

my approach right find conversations of user , try group conversationid:

select distinct conversationid, senderid, receiverid, message, timestamp  message conversationid in       (select conversationid conversation persone = 3 or perstwo = 3) group conversationid order timestamp desc

unfortunately these results:

2   3   8   hi x!   1431680405000 1   1   3   xyz!    1431680294000

even though need allt bra? result last conversation.

i running newest version available arch of mariadb.

a common pattern type of question find last item in derived table , join filter main query. in case query like:

select *  conversation c join message m on c.conversationid = m.conversationid join (   select conversationid, max(timestamp) timestamp    message   group conversationid ) x on m.conversationid = x.conversationid    , x.timestamp = m.timestamp c.persone = 3 or c.perstwo = 3

sample sql fiddle


Comments

Post a Comment

Popular posts from this blog

c++ - Difference between pre and post decrement in recursive function argument -

i have following sample code used pre-decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(--c); cout << c << endl; return; } } this function give output input 4 : dp3 dp2 dp1 dp0 0 1 2 3 but when use post decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(c--); cout << c << endl; return; } } output goes in infinite loop dp4 can explain me in detail why happens ? this happens because function(c--) called same value of c , when finishes c decremented. recursively called, hence called same value no chance of return , hit stack overflow error. assume this, int x = 1, y = 0; y = x++ result y == 1 , x == 2. if y = ++x , bot x , y 2.
Read more

php - Nothing but 'run(); ' when browsing to my local project, how do I fix this? -

i added new project. made mistake in projectname.conf file in sites-available apache2, led me reinstalling apache2. after reinstalling , re-enabling projects on every page of every project .. <body> run(); </body> .. i've run composer update, restarted service, restarted pc, checked config files, tried disabling new project. there nothing in error log, , access.log: 127.0.0.1 - - [15/may/2015:01:40:47 +0200] "get / http/1.1" 304 181 "-" "mozilla/5.0 (x11; ubuntu; linux x86_64; rv:38.0) gecko/20100101 firefox/38.0" maybe i'm forgetting apache2 reinstall? don't think did different last time installed it. looks haven't setup php correctly. take @ this great guide , maybe you're forgetting link php config apache2.
Read more

php - How can I echo out this array? -

i don't know how go grabbing data in variable , put foreach loop. class tree{ private $info = array( array('name'=>'jim','state'=>'nu','company'=>'nu','phone'=>array('cell'=>'5615111111','office'=>'5611111111'),'email'=>array('primary'=>'exs@example.com','ex@there.com')), array('name'=>'joe smith','city'=>'phoenix','phone'=>'4805551111','email'=>'jsmith@some_email.com'), array('name'=>'john doe','city'=>'chandler','company'=>'doe co.','email'=>array('jdoe@gmail.com','personal'=>'email@email.com'),'phone'=>'6025550002') ); } if you're inside of class, can access private variable using $this->variablename . example, i...
Read more