I am working on a social networking project with cassandra. Users can subscribe to a profile and have access to the list of people who have subscribed to that same profile. My goal is to retrieve in a table called user_follows the list of people subscribed to a profile.
CREATE TABLE users_follows (to_id text, from_id text, followed_at timestamp, PRIMARY KEY(to_id, from_id))
The problem is that some profiles can have thousands of subscribers and I don't want to get them all at once. That's why I'd like to get the list in increments of 20 depending on how far down the user goes. My problem is that I can't see how to retrieve the other parts of the list after the first select because Cassandra always returns the same users.
SELECT * FROM users_follows where to_id = 'xxxxx'
A possible solution was to sort with a timestamp but in case I want to retrieve the list of people to whom a user is subscribed (the reverse query) this would not work. One solution would be to use materialized views but I'm not sure that it would be very optimal given the size of the table. Or to create a different table, one user_follows and another user_followers, but I don't think this is very recommended....
I'm very new to FileMaker currently working on a Mac. I've been assigned a new simple system to work towards completing and I have bumped into some issues with database relationships. I've got experience with PHP/MySQL databases connections etc. but FileMaker seems to require a somewhat different mindset and approach.
I'll try to explain this as simply as I can.
Here's the table relationships in my database
What I'm trying to do is a list of "to-do" notes, an interactive menu where the user can add things that needs to be done. I've done this with a portal on a layout based on the table "site". The portal is based on the table "todo_notes", which is connected to site through the "site_id".
Here's what it looks like in browse mode
What I'm having problems with is adding a relationship between the todo_notes and contacts. The contacts are two separate tables called "county_contacts" and "property_owner_contacts". What I want to accomplish is the possibility for the user to, from a dropdown-list, add a single contact from these two tables. Preferably I'd like to sort of merge these two tables into the same dropdown-list.
Let me know if you need any other information or a better explanation of my issue. Any help is very welcome!
If you have a single contacts table with foreign keys for both county and property owner tables, that would let you have a single list for all contacts. From there you could also build a value list based on a relationship, for example to filter only contacts that belong to either county or property owners.
If you then need to further normalize the tables, fields that pertain to either relationship exclusively could be moved to another table from there, as a one to one relationship, if that is a concern.
The Short Answer
You need to create a Contacts table. Filemaker has no way of dynamically generating value lists. Instead, you can base a value list on any field, therefore, the only way of generating a list of the contact names would be if they were all in the same table.
The Long Answer
Because Filemaker only allows us to use ONE field for a value list, we must create a new table for the contact. I would recommend that you replace the two contact tables with a single contact table,(seeing as the fields look the same between the two tables) and then add a toggle on the contact for Owner or County. However, you could also create a single contact table for all of the fields that overlap that has foreign keys to the owner and county tables.
You would then use the fullname field from the contact and be good to go.
That is, assuming that you did not want to filter the contacts at all or only show contacts associated with this site.
To start with, I highly recommend using the Anchor-buoy method for organizing the relationship graph. Here's an explanation of the anchor-buoy method: http://sixfriedrice.com/wp/six-fried-rice-methodology-part-2-anchor-buoy-and-data-structures/ . It's just a convention, but will help you with the idea of context in FileMaker. It's widely accepted among the FileMaker community as the "right" way to organize a relationship graph. I will continue my explanation using this method.
Each Table Occurrence (the boxes in the graphs, or TO) represents a unique context from which you can view and edit information. In the anchor buoy method, each Table only has one "anchor" TO. I would recommend only using anchor TO's for the context of your layouts. Then, your portal, and any other corresponding information, will be on your buoy TO's. Here is what your new portal relationship would look like. You would select fields from your buoy TO's to use in the portal.
The easiest way to filter your value list by only contacts associated with this site would be to create a foreign key from the contact table to the site, and then add a TO to the graph, for the contact table. You would then click "Include only related values starting from" radio button, and specify your new TO.
So im working on a side project involving the Steam API and I am not sure if this would be a suitable and effective way to do what I want.
Basically I have a User model with an inventory field relating to a certain game. I fetch the Users game inventory when they log-in and store the json result within this single field. I have another model which contains the item schema for every item in the game.
Basically I want to relate the information stored within the database for a particular item(item model) to that items information within the json result(inventory items).
I previously tried to save the inventory in a separate table and created a relation between the user, user-inventory and items in this table however the problem with this was ensuring that the inventory stored in my database was the same as that fetched (exactly identical). Under this scenario I would basically need to delete(multiples may exists of the same item) every inventory item and then insert the inventory items retrieved at login back in.
My question is this. Is this an appropriate solution, bad practice or is there a better way to do what i need?
Thanks
Are you sure that you have to delete all of the inventory items and re-add the new ones? Could you iterate through each of the inventory entries and add/update/delete as needed?
I think that the JSON solution would work. It's probably a matter of preference at this point. I always feel like it's nicer to stay with a traditional relational data structure until you really need to optimize. But I don't see why the json wouldn't work. You can create a utility function on your user model that extracts the item ids and fetches all of the related records.
I've been using cakephp for a while, but have not learned all the ins and outs yet so I may be missing something simple. Or the problem may lie with my database structure. Either way, if anyone has any idea of what I'm doing wrong, please share.
Is there a way to order the data returned by cakephp's find using values stored in another table?
I am creating custom form fields on a per category basis, so when I choose a particular category to post in, custom fields will be added to my form. I have 3 tables: Posts, Fields, and Answers. The Posts table stores the basic static information for the post, such as id, category_id, title, and description. The Fields table stores the custom field data, such as category_id, field_label, field size, etc. The Answers table stores the values that are entered for particular fields, such as post_id, field_id, value.
I am trying to display the posts for a particular category, and create html table headers on the fly, using select fields, set by a column toggle in the fields table, and also select the answers associated with that particular field and post.
I am able to select all the data I want, and paginate everything just fine, but what I can't seem to figure out is how to order the data using one of the dynamic column values. For example, if I have year, make, and model as 3 custom fields, I would like to click the year column to sort my results by the year values, and if I click the make column, I would like to sort my results by the make values, etc.
I know how to order the results by a particular field inside the posts table, such as id or title, but is it possible to order using the custom fields? Am I setting up the database and/or something else wrong, and if not is there are particular cakephp method or sql command that I need to use in order to sort by the custom fields? I'm not really well versed in complex sql commands.
Thanks.
I'd suggest you pass the field name and sort direction in the URL (GET param). So when you have your table header link, form it so that it links to a URL as so:
http://somesite.com/pages/index/sort:customfield1/dir:asc
Then when you're grabbing the data from the db in your find() query, include the named parameters as the order parameter that can be sent to find.
You'll need to determine a default sorting column and direction. Maybe have that be selectable with a boolean field in the schema -- if there are no parameters sent to the action above, pull the field from your other table that has default set to true in the record.
To clarify: when a user visits a given action, first you'll pull the custom fields from the other table. Then using those fields (either the default as mentioned above, or the named params passed in the URL) form the query for the actual data, using the order parameter.
I have an application with multiple "pick list" entities, such as used to populate choices of dropdown selection boxes. These entities need to be stored in the database. How do one persist these entities in the database?
Should I create a new table for each pick list? Is there a better solution?
In the past I've created a table that has the Name of the list and the acceptable values, then queried it to display the list. I also include a underlying value, so you can return a display value for the list, and a bound value that may be much uglier (a small int for normalized data, for instance)
CREATE TABLE PickList(
ListName varchar(15),
Value varchar(15),
Display varchar(15),
Primary Key (ListName, Display)
)
You could also add a sortOrder field if you want to manually define the order to display them in.
It depends on various things:
if they are immutable and non relational (think "names of US States") an argument could be made that they should not be in the database at all: after all they are simply formatting of something simpler (like the two character code assigned). This has the added advantage that you don't need a round trip to the db to fetch something that never changes in order to populate the combo box.
You can then use an Enum in code and a constraint in the DB. In case of localized display, so you need a different formatting for each culture, then you can use XML files or other resources to store the literals.
if they are relational (think "states - capitals") I am not very convinced either way... but lately I've been using XML files, database constraints and javascript to populate. It works quite well and it's easy on the DB.
if they are not read-only but rarely change (i.e. typically cannot be changed by the end user but only by some editor or daily batch), then I would still consider the opportunity of not storing them in the DB... it would depend on the particular case.
in other cases, storing in the DB is the way (think of the tags of StackOverflow... they are "lookup" but can also be changed by the end user) -- possibly with some caching if needed. It requires some careful locking, but it would work well enough.
Well, you could do something like this:
PickListContent
IdList IdPick Text
1 1 Apples
1 2 Oranges
1 3 Pears
2 1 Dogs
2 2 Cats
and optionally..
PickList
Id Description
1 Fruit
2 Pets
I've found that creating individual tables is the best idea.
I've been down the road of trying to create one master table of all pick lists and then filtering out based on type. While it works, it has invariably created headaches down the line. For example you may find that something you presumed to be a simple pick list is not so simple and requires an extra field, do you now split this data into an additional table or extend you master list?
From a database perspective, having individual tables makes it much easier to manage your relational integrity and it makes it easier to interpret the data in the database when you're not using the application
We have followed the pattern of a new table for each pick list. For example:
Table FRUIT has columns ID, NAME, and DESCRIPTION.
Values might include:
15000, Apple, Red fruit
15001, Banana, yellow and yummy
...
If you have a need to reference FRUIT in another table, you would call the column FRUIT_ID and reference the ID value of the row in the FRUIT table.
Create one table for lists and one table for list_options.
# Put in the name of the list
insert into lists (id, name) values (1, "Country in North America");
# Put in the values of the list
insert into list_options (id, list_id, value_text) values
(1, 1, "Canada"),
(2, 1, "United States of America"),
(3, 1, "Mexico");
To answer the second question first: yes, I would create a separate table for each pick list in most cases. Especially if they are for completely different types of values (e.g. states and cities). The general table format I use is as follows:
id - identity or UUID field (I actually call the field xxx_id where xxx is the name of the table).
name - display name of the item
display_order - small int of order to display. Default this value to something greater than 1
If you want you could add a separate 'value' field but I just usually use the id field as the select box value.
I generally use a select that orders first by display order, then by name, so you can order something alphabetically while still adding your own exceptions. For example, let's say you have a list of countries that you want in alpha order but have the US first and Canada second you could say "SELECT id, name FROM theTable ORDER BY display_order, name" and set the display_order value for the US as 1, Canada as 2 and all other countries as 9.
You can get fancier, such as having an 'active' flag so you can activate or deactivate options, or setting a 'x_type' field so you can group options, description column for use in tooltips, etc. But the basic table works well for most circumstances.
Two tables. If you try to cram everything into one table then you break normalization (if you care about that). Here are examples:
LIST
---------------
LIST_ID (PK)
NAME
DESCR
LIST_OPTION
----------------------------
LIST_OPTION_ID (PK)
LIST_ID (FK)
OPTION_NAME
OPTION_VALUE
MANUAL_SORT
The list table simply describes a pick list. The list_ option table describes each option in a given list. So your queries will always start with knowing which pick list you'd like to populate (either by name or ID) which you join to the list_ option table to pull all the options. The manual_sort column is there just in case you want to enforce a particular order other than by name or value. (BTW, whenever I try to post the words "list" and "option" connected with an underscore, the preview window goes a little wacky. That's why I put a space there.)
The query would look something like:
select
b.option_name,
b.option_value
from
list a,
list_option b
where
a.name="States"
and
a.list_id = b.list_id
order by
b.manual_sort asc
You'll also want to create an index on list.name if you think you'll ever use it in a where clause. The pk and fk columns will typically automatically be indexed.
And please don't create a new table for each pick list unless you're putting in "relationally relevant" data that will be used elsewhere by the app. You'd be circumventing exactly the relational functionality that a database provides. You'd be better off statically defining pick lists as constants somewhere in a base class or a properties file (your choice on how to model the name-value pair).
Depending on your needs, you can just have an options table that has a list identifier and a list value as the primary key.
select optionDesc from Options where 'MyList' = optionList
You can then extend it with an order column, etc. If you have an ID field, that is how you can reference your answers back... of if it is often changing, you can just copy the answer value to the answer table.
If you don't mind using strings for the actual values, you can simply give each list a different list_id in value and populate a single table with :
item_id: int
list_id: int
text: varchar(50)
Seems easiest unless you need multiple things per list item
We actually created entities to handle simple pick lists. We created a Lookup table, that holds all the available pick lists, and a LookupValue table that contains all the name/value records for the Lookup.
Works great for us when we need it to be simple.
I've done this in two different ways:
1) unique tables per list
2) a master table for the list, with views to give specific ones
I tend to prefer the initial option as it makes updating lists easier (at least in my opinion).
Try turning the question around. Why do you need to pull it from the database? Isn't the data part of your model but you really want to persist it in the database? You could use an OR mapper like linq2sql or nhibernate (assuming you're in the .net world) or depending on the data you could store it manually in a table each - there are situations where it would make good sense to put it all in the same table but do consider this only if you feel it makes really good sense. Normally putting different data in different tables makes it a lot easier to (later) understand what is going on.
There are several approaches here.
1) Create one table per pick list. Each of the tables would have the ID and Name columns; the value that was picked by the user would be stored based on the ID of the item that was selected.
2) Create a single table with all pick lists. Columns: ID; list ID (or list type); Name. When you need to populate a list, do a query "select all items where list ID = ...". Advantage of this approach: really easy to add pick lists; disadvantage: a little more difficult to write group-by style queries (for example, give me the number of records that picked value X".
I personally prefer option 1, it seems "cleaner" to me.
You can use either a separate table for each (my preferred), or a common picklist table that has a type column you can use to filter on from your application. I'm not sure that one has a great benefit over the other generally speaking.
If you have more than 25 or so, organizationally it might be easier to use the single table solution so you don't have several picklist tables cluttering up your database.
Performance might be a hair better using separate tables for each if your lists are very long, but this is probably negligible provided your indexes and such are set up properly.
I like using separate tables so that if something changes in a picklist - it needs and additional attribute for instance - you can change just that picklist table with little effect on the rest of your schema. In the single table solution, you will either have to denormalize your picklist data, pull that picklist out into a separate table, etc. Constraints are also easier to enforce in the separate table solution.
This has served us well:
SQL> desc aux_values;
Name Type
----------------------------------------- ------------
VARIABLE_ID VARCHAR2(20)
VALUE_SEQ NUMBER
DESCRIPTION VARCHAR2(80)
INTEGER_VALUE NUMBER
CHAR_VALUE VARCHAR2(40)
FLOAT_VALUE FLOAT(126)
ACTIVE_FLAG VARCHAR2(1)
The "Variable ID" indicates the kind of data, like "Customer Status" or "Defect Code" or whatever you need. Then you have several entries, each one with the appropriate data type column filled in. So for a status, you'd have several entries with the "CHAR_VALUE" filled in.