Mysql query to search same column in different tables -


i have 3 tables

table_a

 ╔════╦══════╗  ║ id ║ mid  ║  ╠════╬══════╣  ║  1 ║ 5996 ║  ║  2 ║  148 ║  ║  3 ║  101 ║  ║  4 ║ 5636 ║  ║  5 ║  143 ║  ║  6 ║  101 ║  ║  7 ║  959 ║  ║  8 ║  148 ║  ╚════╩══════╝

table_b

 ╔════╦══════════════╦══════╗  ║ id ║  community   ║ mid  ║  ╠════╬══════════════╬══════╣  ║  1 ║ jeff atwood  ║ 5636 ║  ║  2 ║ geoff dalgas ║  148 ║  ║  3 ║ neal  marley ║  101 ║  ║  4 ║ joel spolsky ║  959 ║  ╚════╩══════════════╩══════╝

table_c

 ╔════╦══════════════╦══════╗  ║ id ║  community   ║ mid  ║  ╠════╬══════════════╬══════╣  ║  1 ║ jim atwood   ║ 3212 ║  ║  2 ║ rim  dalgas  ║  428 ║  ║  3 ║ jarrod dixon ║  388 ║  ║  4 ║ noel spolsky ║  339 ║  ╚════╩══════════════╩══════╝

i can use plain mysql query. need join table_a table_b find community , in case there no community corresponding mid in tablea need join table_c community.how accomplish that? please me.thank you!

you can use left join both tables , select first existing item using coalesce:

select a.id, a.mid, coalesce(b.community, c.community, '') community table_a      left join table_b b on a.mid = b.mid     left join table_c c on a.mid = c.mid

in case if have matching data in table_b, b.community used, otherwise if there matching data in table_c, c.community used. if there no match in either of tables, empty space used.


Comments

Post a Comment

Popular posts from this blog

c# - Validate object ID from GET to POST -

i have method allows user access comment have made on site. have post method lets them update comment. my normal solution send entire comment model through, let them update it, update on database when post back. involve sending commentid through in hiddenfor , can manipulated. how can verify commentid sent in get method same i'm getting in post , not able alter comment wish? how can verify commentid sent in method same i'm getting in post? basically have validate following things in post - user logged-in user. authenticated users post comments. commentid in post , should valid commentid , should present in database. userid associated logged-in user should same userid associated comment . comment should contain userid column, can check @ time of update. to make sure update happens comment has been sent in get - hold commentid in session , in post action compare commentid value in session .
Read more

node.js - Custom Model Validator SailsJS -

when using custom model validator checks record within model. return within spread doesn't seem end control flow. //post.js model /** * custom validator **/ types: { isuservalid: function(user_id) { var promise = require('bluebird'); promise.all([ user.findone({id: user_id}) ]) .spread(function(user) { console.log(user); if (user === null || user === undefined) { console.log('failed'); return false; }else{ console.log('passed'); return true; } }); } }, my response standard validation failed response. { "error": "e_validation", "status": 400, "summary": "1 attribute invalid", "model": "post", "invalidattributes": { "owner": [ { "rule": "isuservalid", ...
Read more

php - Find a regex to take part of Email -

i have following emails need extract part from: bestellnummer xxx: 1 von xxx, 1er pack ------------- anfang der nachricht ------------- foo bar baz foo bar baz // <<<<< need text here ------------- ende der nachricht ------------- ------------- anfang der nachricht ------------- foo bar baz foo bar baz ------------- ende der nachricht ------------- there 0 unlimited occurences of ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- and i'm able extract first part regex: $re = "/------------- .*? -------------.?(.*?).?------------- .*? -------------/s"; but, i'm quite new on learning regex, i'm pretty sure there must better regex extract part (foo bar baz foo bar baz) of text between ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- as can in different languages, i'm using .? to match between hyphens. i...
Read more