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29 views

Usage of non standardized queries

So this is more of a theory question than practical but I'd appreciate any help. My friend and I are doing a project to learn new stuff and have fun. He's a coder and I like to think that I'm good ...
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115 views

How to merge rows based on how much data they have?

I am cleaning data and I formed a table something like this: file | product | color | product_id --------------------------------------------- one.csv pipe blue null ...
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49 views

Where should a default setting field be?

I am creating a database to track occurrences of incidents on buses based on an existing system. Currently the drivers can set a default bus number, which is used to pre-populate the bus number on the ...
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442 views

Closure of attributes definition clarification

A databases book I am using states [1]: The closure of {A1, A2, ..., An} under the FD's in S is the set of attributes B such that every relation that satisfies all the FD's in set S also satisfies ...
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Method to economically insert Bill of Materials BOM items into a Stock Table?

I’m new to the wonderful world of database design and I’m currently experimenting with an implementation for my little brother relating to Model Train Sets. [I will be using SQL Server 2012 / Asp.Net ...
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Using logic or in relational algebra

In relational algebra I can obtain the courses taught in Fall 2009 or Spring 2010 with Π_{course_id} (σ_{semester=“Fall” Λ year=2009} (section)) ∪ Π_{course_id} (σ_{semester=“Spring” Λ year=2010} ...
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Canonical Cover for Functional Dependencies ho

I'm trying to decompose a relation into 3NF and I'm given the following information: Given R(A B C D E F G H I) Keys: {A,B} {A,D},{B,D} FDs: AB-> DE A->I B->CFGH G->H AD->BCEFGH ...
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Translating duplicated data entries into Domain Relational Calculus

Given a following table named BOOKING, which contains three columns, guest_name, room_number and booking_date, how do I find the all the guest_name that have the same room_number and booking_date? I ...
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Examples of a database with no consistency measures that ensures consistency through schema alone

To clarify, the database can be any type RDBMS, NoSQL/BigTable. However, it must not employ any usual consistency measures such as locks, or synchronization, but the inconsistency-invincibility must ...
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108 views

In DBMS binary relationship is better than ternary

For which reasons (Features/points) binary relationship is better than ternary one in Database ER modeling? I got something by searching in website but those are not precise and meaningful!