references :
https://www.firebase.com/blog/2013-10-01-queries-part-one.html
https://www.firebase.com/blog/2014-01-02-queries-part-two.html
https://www.firebase.com/docs/javascript/query/startat.html
https://www.firebase.com/docs/javascript/firebase/endat.html
example by kato
http://jsfiddle.net/katowulf/vQEmt/2/
where at firebase
startAt + endAt uses .priority field to query the nodes, firstly I used to store the dateCreated to .priority… great then at code with just a .startAt, I grab the needed…
Later, a need occurred, to list the nodes also via another field, contacted firebase support the reply was :
few different approaches here:
1) Merge category and priority into one string and set that as the priority of the records
2) Create an index of records by category and iterate that list to grab them by ID.
3) Try ElasticSearch, which is nearly plug-and-play with Firebase, to look up records by complex criteria. Check out our blog post on this.
ok, I proceed with 1) so now, I have something like :
so I started to make examples to understand how works, the need is to list [from - to] period + specific country :
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*1*
.startAt('Afghanistan')
.endAt('Afghanistan');
//no result
*2*
.startAt('Afghanistan1390383000')
.endAt('Afghanistan1390383000');
//I got 1row
*3*
.startAt('Afghanistan1190383000')
.endAt('Afghanistan1290383000');
//no result
*4*
.startAt('Afghanistan1290383000')
.endAt('Afghanistan1390383000');
//I got 1row
*5*
.startAt('Afghanistan1290383000')
.endAt('Afghanistan1390382000'); //the last 3000 to 2000
//no result
conclusion store first the text field then the UTC, the previous queries saw us that can handle the alphanumeric using startAt and endAt!
origin - http://www.pipiscrew.com/?p=727 firebase-query-by-priority