I am designing an application where an account holder has "friends". How would I go about linking those friends to the original account holder? Would an efficient SQL table be something like:
AccountHolderID (varChar 20)
FriendsID (nText)
We implement something similar--using a table to hold the friends... Ours breaks down quite simply as a table of friends...
AccountHolderId( type)
FriendAccountHolderId ( type)
Created(datetime) // useful for tracking when the friend was added
Both of the Id fields link back to the Accounts/Users table.
Related
View StructureI am working on a tool wherein we have to configure a view to send out the custom email notifications to the customers.
I have a view name:
webNotification_Mail_LiqAmt_Workflow which stores email details like
Then I have another table from where I need to bring in the amount which is to be mailed to the customers based on their projects and other parameters.
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I do not need email setup because it is already taken care. I need to pass the amount in the email body so basically I need to get the amount in 'messsge' column of the above view (webNotification_Mail_LiqAmt_Workflow)
I cannot think of a way to built this logic as both the tables are un-related.
Please help.
Design of the view:
**CREATE VIEW [dbo].[webNotification_Mail_LiqAmt_Workflow]
AS
SELECT ID,
Event,
EmailFrom,
Subject,
Message,
'NoReply#xyz.com' AS EmailTo,
'123#rte.com' AS EmailBCC
FROM dbo.webWorkflowNotification_LiqAmt**
I would need custom amounts in the message column based on the parametrers.The view that from where I need the Amounts looks like:
SELECT TOP (1000) [LIQAMTID]
,[Project_Name]
,[Startup]
,[Business_contact_Name]
,[Business_Contact_Email]
,[Sum_Liq_amt]
FROM [webLiqAmt_Mail_Notification]
According to my grasp of the situation I guess what you are looking for is a cross join.By using cross join you could add the two unrelated tables and then later exploit them for your use. I am giving and example,
SELECT username,password,dob,address
FROM basic_details
CROSS JOIN login
where username and password belong to login, and dob and address belong to basic_details.
OR
You can use cartesian product of the two tables.
SELECT * FROM basic_details, login
This would result in M * N rows.
Hope it helps.
I have this table used when a user writes a note.
When writing a note, the user specifies if a sell-department and/or a buy-department should receive the note.
Each user can create a Case (lets say its just a table with case_id and case_text). And the notes the users write are related to a case.
So the table NOTES is (postgres database) something like this:
ID
TEXT (the message itself)
USER_ID (the user that writes the note)
CASE_ID (the case_id for which the note is been written)
Short word about users:
There are "ordinary" users and those working on a department. This should not make big difference for the description here.
When an ordinary user writes a note, let's say he want both buy-department and sell-department to be included (being informed about the note/see the note).
What happens now is that there is another table called UserNotes. It looks like this:
ID
IS_READ
NOTE_ID
USER_ID
DEPARTMENT_ID
READ_AT_DATE
So ordinary user with id = 1 writes this note and in the code (as he tells sell and buy-departments have to be included) I search for all the users working at that specific sell-department and all those working at that specific buy-department. I then put all these users in the table UserNotes. With IS_READ false by default.
When a user in the specific sell-department reads the note, I will then change IS_READ for this user's entry in UserNotes.
This is how it works today. I don't think this is scalable. I'm already getting performance issues. I don't think it is important to know when a note has been read. So because of this I was thinking that maybe the following solution could work. Please have a look and tell me if it could be better and the current one or if you have some other suggestion please let me know:
I drop UserNotes table. I add a new filed in table Notes: READ_BY. Here I will update the field each time a user reads the note.
I don't know if I could use some postgres-specific thing, maybe making this field a json-string and searchable.
.Hi i'm working with Asp and SQL-Server and i have no problem with writing dynamic query
I'm trying to Write a search page for searching people.
I have 3 related tables:
See my table diagram in : http://tinypic.com/r/21159go/5
What i'm trying to do is to design a search page that a person can search users with a dynamic number of attributes.
Example:
think that a username called "User1" has 3 attributes named "Attr1", "Attr2" and "Attr3" related to him in "UserAttributes" table and "User2" has 3 attributes named "Attr1", "Attr2" and "Attr4".
Attribute names and other bunch of items unrelated to search function saved in "Attributes" Table. This is because i want to relate an attribute between multiple users. and their values are stored in "UserAttributes" table.
Well someone wants to search upon "Attr1" and "Attr2" and wants to return all users that have "Attr1" and "Attr2" with specific value.
I need a query to know how to implement this. I can write a dynamic query with asp.net so if someone please give me a query for this one example i have brought, i would be thankful
P.S. This is not my real database. my real database is much more complex and has more fields and tables but i just cut it and brought only necessary items. and because attributes are very dynamic they can't be embedded in table columns.
Thanks in advance
Based on your DB diagram your code would be something like this
update:
SELECT u.*
FROM users AS u
LEFT OUTER JOIN UserAttributes AS ua1
ON u.USER_ID = ua1.USER_ID
LEFT OUTER JOIN UserAttributes AS ua2
ON u.USER_ID = ua2.USER_ID
WHERE (
ua1.attribute_id = 'att1'
AND ua.attribute_value = 'MyValue' )
AND (
ua2.attribute_id = 'att2'
AND ua.attribute_value = 'MyValue2' )
In where clause you would specify the attirbute_Id and what value you are expecting out of it. Than just decide if you want to restrict users to have all values match or just one of them, in that case modify AND between statements to be OR
if you just want to do this quick and dirty you can create your own class library that can create adhoc sql that will pass to the database.
if you want more organized matter, create SP that will bring back users and accepts any left of id and value. Do a lot of that by passing list separated by comma, colon or semicolon. Than split it up in SP and filter results based on those values
there are many other alternatives like EntityFramework, LINQ-to-SQL and other options, just need to figure out what works best for you, how much time you want to spend on it and how easy will it be to support later.
I'm currently logging all actions of users and want to display their actions for the people following them to see - kind of like Facebook does it for friends.
I'm logging all these actions in a table with the following structure:
id - PK
userid - id of the user whose action gets logged
actiondate - when the action happened
actiontypeid - id of the type of action (actiontypes stored in a different table - i.e. following other users, writing on people's profiles, creating new content, commenting on existing content, etc.)
objectid - id of the object they just created (i.e. comment id)
onobjectid - id of the object they did the action to (i.e. id of the content that they commented on)
Now the problem is there are several types of actions that get logged (actiontypeid).
What would be the best way of retrieving the data to display to the user?
The easiest way out would be gabbing the people the user follows dataset and then just go from there and grab all other info from the other tables (i.e. the names of the users the people you're following just started following, names of the user profiles they wrote on, etc.). This however would create a a huge amount of small queries and trips to the database in a while loop. Not a good idea.
I could use joins to retrieve everything in one massive data set, but how would I know where to grab the data from in just one query? - there's different types of actions that require me to look into several different tables to retrieve data, based on the actiontypeid...
i.e. To get User X is now following User Y I'd have to get my data (User Y's username) from the followers table, whereas User X commented on content Y would need me to look in the content table to get the content's title and URL.
Any tips are welcome, thanks!
Consider creating several views for different actiontypeids. Union them to have one full history.
Entities
We have an entity called Product which is loaded using NHibernate.
Product has a category which NHibernate happily populates for me.
Database
In the database, Product has a foreign key for category.
Scenario
User edits this Product (via a web interface) and chooses a different category (say instead of "Fish" we select "Veg").
This is probably a dropdown list, with each category shown. When they choose a different category we get an int key.
Problem
Obviously we now want to save the changes to Product but in effect the only change is to save a new int (say 2, instead of 1).
So we retrieve the existing Product, and now comes the problem.
We don't have a "CategoryID" field on Product, we only have a Category property.
But we don't really want to retrieve the category (by id) just to assign it to the Product.
So I guess what I want to know is should we...
a) Add a CategoryID property to Product
b) Create a new category, assign it the relevant id and attach that to Product (but surely that will cause errors, or overwrite the existing category)
c) Retrieve (lookup) the category from the system (by id) and attach that to the Product
d) Do something else entirely!
It looks like you might be able to using the Session.Load(id) functionality.
Session.Load is a special method that returns a proxy with the ID until you request another property at which point it loads. It throws an error if there is no item matching the ID. Try something like:
product.Category = Session.Load<Category>(2); //2 being the new category ID
Session.SaveOrUpdate(product);
I just did a little testing and it did not seem to pull back the entire Category.
Updated: Session.Load is the correct answer
product.Category = session.Load<Category>(2);
session.Save(product);
Use NH's EnumStringType<T> to map your Category as an enum to the respective database value (which can be a string or a number). You'll find quite a few usage examples, if you google for it.
HTH!