mysql - Delete rows using JOIN -


i have 2 tables like:

offlineconversations

userid | messageid  100      15 100      16 100      17

messages

messageid | sentby | message               | convid 15          200      "hi userid 100!"       hash 16          200      "hi again 100!"        hash 17          300      "hi user 300 :)"  hash

so here, userid 100 received 3 messages, user 200 , 300 (determined sentby in messages table.

what want do, deleted rows in offlineconversations, message sent user id 200, sentby 200 in messages. messageid in offlineconversations table associated messageid in messages offlineconversations left with:

userid | messageid 100      17

so basically, delete offlineconversations rows userid 100 , sentby (200) associated them.

convid used history aspects. if de-activates account, rows messages should not deleted. if user deletes account entirely, rows should deleted offlineconversations , messages well. 1 know can cascading pointed out in comments.

thanks

this query should work:

 delete t.*   offlineconversations t   join messages m   on m.messageid = t.messageid   m.sentby = 200 , t.userid = 100;

fiddle

if need delete messages also:

 delete t.*,m.*   offlineconversations t   join messages m   on m.messageid = t.messageid   m.sentby = 200 , t.userid=100;

fiidle


Comments

Post a Comment

Popular posts from this blog

apache - Remove .php and add trailing slash in url using htaccess not loading css -

i have add following code htaccess file removing .php extension , add trailing slash urls. worked fine reduced page loading speed , css code not loading @ all. pages ugly. please help rewriteengine on rewritebase / ## hide .php extension snippet # externally redirect /dir/foo.php /dir/foo rewritecond %{the_request} ^[a-z]{3,}\s([^.]+)\.php [nc] rewriterule ^ %1/ [r,l] # add trailing slash rewritecond %{request_filename} !-f rewritecond %{request_uri} !/$ rewriterule . %{request_uri}/ [l,r=301] # internally forward /dir/foo /dir/foo.php rewritecond %{request_filename} !-d rewritecond %{request_filename}.php -f rewriterule ^(.*?)/?$ $1.php [l] we can rewrite urls using .htaccess files. before writing in .htaccess files need verify kind of server using. can check server adding a <?php phpinfo(); ?> in php page. ensure mod_rewrite module enabled in apache server. can identified checking phpinfo included page. common methods used url rewriting follows ...
Read more

inno setup - TLabel or TNewStaticText - change .Font.Style on Focus like Cursor changes with .Cursor -

is possible change .font.style on focus tlabel or tnewstatictext happens cursor when use .cursor ? there no built-in support track mouse hovering in inno setup @ time. however, intercepting window procedure of controls can track yourself. following example need innocallback library: [setup] appname=my program appversion=1.5 defaultdirname={pf}\my program outputdir=userdocs:inno setup examples output [files] source: "innocallback.dll"; destdir: "{tmp}"; flags: dontcopy [code] #ifdef unicode #define aw "w" #else #define aw "a" #endif const gwl_wndproc = -4; wm_mousemove = $0200; type wparam = uint_ptr; lparam = longint; lresult = longint; twindowproc = function(hwnd: hwnd; umsg: uint; wparam: wparam; lparam: lparam): lresult; function setcapture(hwnd: hwnd): hwnd; external 'setcapture@user32.dll stdcall'; function releasecapture: bool; external 'releasecapture@user32.dll stdcall'; func...
Read more