SQL: Multiple Foreign Keys for Inheritance -


i have few tables in database , have quick question regarding foreign keys.

tables

company

pk: companyid

manufacturer

pk, fk: companyid

make/model

pk: makemodelid fk: manufacturerid

equipment

pk: equipmentid fk: makemodelid

would proper include manufacturerid column fk manufacturer in equipment table? , smart create index on both manufacturerid , makemodelid in equipment table? i'm self taught , seeking design input. thanks.

no, not proper include fk manufacturer table in equipment table.

the equipment table has fk make/model table has fk manufacturer table. if created fk, technically record in equipment table linked 2 different manufacturers.


Comments

Post a Comment

Popular posts from this blog

php - get table cell data from and place a copy in another table -

two-part question: have 2 tables: 1 table items , other table selected items copied when add button clicked. after, when items wanted selected, there 'finished' button post items selected db. i started javascript didn't far @ because jquery seems better suited i'm not familiar it function addto() { var div = document.getelementbyid('fixeddiv','inside'); div.innerhtml = div.innerhtml + 'item added'; } <div id='fixeddiv'> <table align="center" id="tradee"> <th rowspan="2"> other item</th> <?php while($rowi =$item->fetch_assoc()) {?> <tr> <td> <?php echo $rowi['item_name']; ?> </td> <td><?php echo $rowi['item_description'];?></td> </tr> <?php } ?> </table> <br> <table align="center" id="tradetable"
Read more

javascript - Mootools wait with Fx.Morph start -

i trying var effect = new fx.morph(testmorph, { wait/delay 2 seconds before starting. ( fiddle here ) but when try .wait(2000) or .delay(2000) , or .wait(2000, effect) uncaught typeerror: object [object object] has no method 'delay' any ideas how working? code i'm using: var testmorph = document.id('testmorph'); var effect = new fx.morph(testmorph, { transition: 'back:out', duration: 900, link: 'chain' }).start({ 'top': 20, 'opacity': 1 }).start({ 'border-color': '#a80025', 'color': '#a80025' }); effect.delay(2000); you can use combination of chain() , delay() achieve desired effect. new fx.morph(testmorph, { transition: 'back:out', duration: 900, link: 'chain' }).start().chain(function(){ this.start.delay(2000,effect,{ //first }); }).chain(function(){ this.start({ //second }); }); the
Read more

php - Navigate throught databse rows -

i run image hosting site, , ive run problem. want make 2 buttons beside pic "next image" , "prev image". im new php/mysql , haveing troubles. check out got. use id (numbers) find correct row, have image name build next link. how make below query next , prev image names + ids? $query_next = ("select imageid, image_name images image_name = '$image_main' order imageid desc limit 1"); $query_prev = ("select imageid, image_name images image_name = '$image_main' order imageid asc limit 1"); // next $next = mysql_query($query_next); // prev $prev = mysql_query($query_prev); while ($row = mysql_fetch_assoc($next)) { $next = $row['image_name']; } while ($row = mysql_fetch_assoc($prev)) { $prev = $row['image_name']; } the html = > simple stuff. <a href="http://mysite.com/view_image/<?=$next?>">next image</a> <a href="http://mysite.com/view_image/<?=$pr
Read more