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read only certain fields in firebase
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Closed 3 years ago.
Pertaining to the video by Firebase below, I have the following question- I have not received a response on YouTube yet, and was wondering if anyone here knows of a possible solution.
https://www.youtube.com/watch?v=sKFLI5FOOHs
In General I want to be able to know how to query data for selected items, and not all data in a set.
Specific Question: Instead of pulling all entries in a child ref, how can we select specific entries (key & value) from the data in Firebase? I'm having bad luck nesting with orderByChild() & I believe would need the on value listener event he began to mention.
For Example (#2): SELECT Name from Users WHERE email = "alice#email.com" instead of SELECT * from Users WHERE email = "alice#email.com"
This is not possible with the client SDKs. When you receive a node, you will get all of its children every time.
If you need to limit the amount of data from a query, you will have to split the parent node into separate nodes that contain only the data for a desired query. Sometimes people duplicate data into different nodes just to create special queryable nodes for a specific purpose. This is fairly common to do with NoSQL type databases, and it's called data denormalization.
Related
I'm new to MS Access and am trying to speed up a data gathering process that is taking forever in Powershell. In Powershell I have 10 or so web API calls to get data and each comes back as an object with multiple properties (fields.) Each set of data has related fields to 1 or more of the other sets of data. Getting the data is very quick but piping an array of objects to where-object to select-object takes over an hour and there's really not that much data. Each object contains 500-1500 "records" and 5 to 10 "fields" so I thought why not export that data and use something that's intended to search through data to do the job? I exported each object as a separate .CSV file. So enter MS Access..
I imported each of the CSV's as a separate table (easy enough.) I'm going to simplify this down for this example to the following 3 tables:
[Tables]https://i.stack.imgur.com/UCH1F.jpg
Every table has fields that relate it over to other tables. Pretty much there's some sort of Id field in every table that is related to another Id field in a different table that I need to pull a field called "name" from. I'm trying to follow the bread crumbs from the Player name to it's Network name to it's Application name, to it's Layout name, etc... I want to build a query that I would eventually just be able to export as an Excel file. I also would prefer to just write out the SQL unless it's really easier to to understand the visual query builder. I'm looking to build a sheet with the following information:
Player's Name would include all names from the Players table and getting just that data makes sense to me. SELECT Name AS PlayerName FROM Players Everything else, not so much. I feel like this will end up being some mega query as I get deeper into related table after related table. In Excel, it would be straightforward using Vlookups across tabs but that doesn't seem to be the best approach. Given the info above, I'm trying to achieve the following output:
Result table
Any help with strategy and syntax greatly appreciated!
You're looking for the JOIN clause.
SELECT
Players.Name PlayerName, Networks.Name PlayerNetwork, Applications.Name ApplicationName
FROM
Players
LEFT OUTER JOIN
Networks
ON
Networks.ID = Players.NetworkId
LEFT OUTER JOIN
Applications
ON
Applications.Id = Players.ApplicationID
I'm facing a very strange issue in my Splunk search. I have a data input coming from a REST API that returns a multi-level (nested) JSON response:
The entity node has several nodes, each node represents one access point. Each access point contains a field called ipAddress.
This API is being called every 5 min and response stored in Splunk. When I do a search to get the list of IP Addresses from one event I don't get all of them. For some reason, is like Splunk is reading only the first seven nodes inside entity, because when I do:
source="rest://AccessPointDetailsAPI" | head 1
Splunk shows only the following values on the field (7 values although there are around 27):
I'm using demo license if that matters. Why I cannot see all values ? If I change my search to look for a specific iPAddress on the response but not on the list it won't return records.
Thanks and regards,
I think I understand the problem now. So the event is a big json and Splunk is not properly parsing all fields on the big json.
We need to tell splunk to parse the specific field we need with spath and specifying the field:
yoursearch | spath output=myIpAddress path=queryResponse.entity{}.accessPointDetailsDTO.ipAddress | table myIpAddress
http://docs.splunk.com/Documentation/Splunk/5.0.4/SearchReference/Spath
But I think also is important to analyze if maybe the data input needs to be divided in multiple events rather than a single huge event.
I have few tables as shown below
Polls
PollId Question Option
1 What 1
2 Why 4
Updates
UpdateId Text
1 Sleep
2 Play
Polls and updates are just two sample tables (In reality there are more tables like ,photos, videos,links etc). But when a user visit his home (like facebook new feed) he must be displayed with data relevant to him (no such data included in this example). ie I want to select data from all tables with less number of query executions. (ie, I want to present a mixture of datas, ie polls, photos, videos etc )
Currently, I'm fetching only ids and type (ie which table) from all of the tables and gather further data while iterating through this resultset. (ie from c# calling another SqlQuery) .
Is there a way to query the data from whole tables at once? (OUTER JOIN?, UNION?)
Or simply,
How can I select different type of entities at once in a single sql Query?
You could write your query so that you have one long select list for everything you want and it all comes back in one result set but I suspect that wouldn't work too well because you might have varying numbers of different types of items per user.
If you really must have it all in one hit then you can issue multiple queries in one go and get multiple result sets back. To handle this you can use an ADO.Net DataSet. See this SO example (but not the accepted answer - see Vikram Dibyal's answer as that gives a very basic overview of what I think you're asking for).
I won't copy and paste the stuff from the linked thread, just head over and take a look.
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We have a business process that requires taking a "snapshot" of portions of a client's data at a point in time, and being able to regurgitate it later. The data set has some oddities though that make the problem interesting:
The data is pulled from several databases, some of which are not ours.
The list of fields that could possibly be pulled are somewhere between 150 and 200
The list of fields that are typically pulled are somewhere between 10 and 20.
Each client can pull a custom set of fields for storage, this set is pre-determined ahead of time.
For example (and I have vastly oversimplified these):
Client A decides on Fridays to take a snapshot of customer addresses (1 record per customer address).
Client B decides on alternate Tuesdays to take a snapshot of summary invoice information (1 record per type of invoice).
Client C monthly summarizes hours worked by each department (1 record per department).
When each of these periods happen, a process goes out and fetches the appropriate information for each of these clients... and does something with them.
Sounds like an historical reporting system, right? It kind of is. The data is later parsed up and regurgitated in a variety of formats (xml, cvs, excel, text files, etc..) depending on the client's needs.
I get to rewrite this.
Since we don't own all of the databases, I can't just keep references to the data around. Some of that data is overwritten periodically anyway. I actually need to find the appropriate data and set it aside.
I'm hoping someone has a clever way of approaching the table design for such a beast. The methods that come to mind, all with their own drawbacks:
A dataset table (data set id, date captured, etc...);
A data table (data set id, row number, "data as a blob of crap")
A dataset table (data set id, date captured, etc....);
A data table (data set id, row number, possible field 1, possible field 2, possible field 3, ...., possible field x (where x > 150)
A dataset table (data set id, date captured, etc...); A field table (1 row per all possible field types); A selected field table (1 row for each field the client has selected); One table for each primitive data type possible (varchar, decimal, integer) (keyed on selected field, data set id, row, position, data is the single field value).
The first being the easiest to implement, but the "blob of crap" would have to be engineered to be parseable to break it down into reportable fields. Not very database friendly either, not reportable, etc.. Doesn't feel right.
The second is a horror show of columns. shudder
The third sounds right, but kind of doesn't. It's 3NF (yes, I'm old) so feels right that way. However reporting on the table screams of "rows that should have been columns" problems -- fairly useless to try to select on outside of a program.
What are your thoughts?
RE: "where hundreds of columns possible"
The limitations are 1000 columns per table
http://msdn.microsoft.com/en-us/library/ms143432.aspx
I'm trying to find the best way to query both news feed and wall using a single request.
First attempt:
Query me/home and me/feed in batch request.
Problem: querying me/home gives me bad results due to Graph API bugs (showing blocked items and on the contrary not showing some items that should be shown) so I decided to change to FQL which seems to handle it much better.
Second attempt:
Use single batch request to query:
(1) me/feed directly.
(2) fql.query for stream table with filter_key set to 'others'.
Problem: Needs to also query for user names because the stream table contains only ids.
Third attempt:
Use batch request to query:
(1) me/feed directly
(2) fql.multiquery for stream table with filter_key set to 'others' and the names table with "WHERE id IN (SELECT actor_id FROM #stream)".
Problem: Fails. It returns "Error: batch parameter must be a JSON array" although it is a json array.
Fourth Attempt:
Use fql.multiquery to get news feed stream, wall stream and names.
Problem: I have no idea how to get a view similar to me/feed using FQL. The best I could get is a list of all my own posts but it doesn't show photos the user is tagged in (so I guess more things are missing).
Appreciate any hints.
Due to FQL not doing SQL style joins, getting information from multiple tables in one query is currently impossible.
Use FQL on the stream table to get the list of posts you want to display be sure to grab the source_id. The source_id can be a user id, page id, event id, group id, and there may be more objects too, just don't remember off the top of my head. (You may also want to do similar caching of the actor_id, target_id and viewer_id)
Cache the source_ids in a dictionary style data cache with source_id being the PK.
Loop thru the cache for ones you don't have information on
Try grabbing the information from the user table based upon id, then next the page table, then event table, and group table until you can find what that ID belongs to. Store the information in your cache
For display merge together the stream table items with the source_id information.