If I have a schema say R={A,B,C,D} and functional depen开发者_如何学Cdencies say {B->C, D->A} will my set of candidate keys be {B,D} or {BD}?If B were a candidate key, you\'d have to be able to
This is a question that arose from the consequences of another question here: Is it better to have two separate user tables or one?
I\'m looking for a clear, basic explanation of the concept of theta join in relational algebra and perhaps an example (using SQL perhaps) to illustrate its usage.
Here is the scenario. STUDENT, FACULTY are sub-classes ofPERSON entity, and they have specialized attributes.
How well an idea are multi-valued attributes in a relational database when they are to be referred extensively?
I have two models: First: class CountryList < ActiveRecord::Base has_one :country, :dependent => :nullify
I have an XML file from a few datasets which I need to store in a Relational DB, say MySQL. The DB schema shld be created based on the fields of the XML file automatically.
I want to create a Grocery List Table that will accept both the Category and the Specific Products. For Example: I add to my grocery list:
I need to add per-province/state taxes to my project. I\'m debating whether I should add a many-to-many relationship between Provinces and Taxes, or just add a tax1_name, tax1_rate, tax2_name, tax2_r
i have a table with two foreign keys as composite key. ActivityTbl - (activityNbr(PK), supervisor(FK), status, type, startDate, endDate, location )
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