Tagged Questions

2
votes
3answers
718 views

How to create multiple one to one's

I have a database set up with many tables and it all looks good apart from one bit... Inventory Table <*-----1> Storage Table <1-----1> Van Table ^ ...
7
votes
5answers
4k views

designing database to hold different metadata information

So I am trying to design a database that will allow me to connect one product with multiple categories. This part I have figured. But what I am not able to resolve is the issue of holding different ...
156
votes
7answers
17k views

When and why are database joins expensive?

I'm doing some research into databases and I'm looking at some limitations of relational DBs. I'm getting that joins of large tables is very expensive, but I'm not completely sure why. What does the ...
39
votes
6answers
18k views

Pros/cons of document-based databases vs. relational databases

I've been trying to see if I can accomplish some requirements with a document based database, in this case CouchDB. Two generic requirements: CRUD of entities with some fields which have unique ...
27
votes
5answers
8k views

Relational table naming convention

I'm starting a new project and would like to get my table- and column names right from the start. For example I've always used plural in table names but recently learned singular is correct. So, if I ...
2
votes
2answers
1k views

How to Implement Referential Integrity in Subtypes

I have the following tables in a relational database: [Sensor] LocationId [PK / FK -> Location] SensorNo [PK] [AnalogSensor] LocationId [PK/FK -> Sensor] SensorNo [PK/FK -> Sensor] ...
2
votes
2answers
165 views

What is the best design for a database table that can be owned by two different resources, and therefore needs two different foreign keys?

My application has notification settings for users that can belong to groups. A group administrator can define settings for the entire group, so that when any user performs an action, the ...
5
votes
3answers
1k views

Opinions on sensor / reading / alert database design

I've asked a few questions lately regarding database design, probably too many ;-) However I beleive I'm slowly getting to the heart of the matter with my design and am slowly boiling it down. I'm ...
20
votes
4answers
17k views

Still Confused About Identifying vs. Non-Identifying Relationships

So, I've been reading up on identifying vs. non-identifying relationships in my database design, and a number of the answers on SO seem contradicting to me. Here are the two questions I am looking ...
39
votes
8answers
14k views

Storing time-series data, relational or non?

I am creating a system which polls devices for data on varying metrics such as CPU utilisation, disk utilisation, temperature etc. at (probably) 5 minute intervals using SNMP. The ultimate goal is to ...
53
votes
7answers
6k views

When shouldn't you use a relational database? [closed]

Apart from the google/bigtable scenario, when shouldn't you use a relational database? Why not, and what should you use? (did you learn 'the hard way'?)
21
votes
3answers
9k views

How can I find MAX with relational algebra?

Working with databases, how can I find MAX using relational algebra?
19
votes
7answers
3k views

Are document-oriented databases meant to replace relational databases?

Recently I've been working a little with MongoDB and I have to say I really like it. However it is a completely different type of database then I am used. I've noticed that it is most definitely ...
24
votes
8answers
11k views

What are the uses for Cross Join? [closed]

A cross join performs a cartesian product on the tuples of the two sets. SELECT * FROM Table1 CROSS JOIN Table2 Which circumstances render such an SQL operation particularly useful?
23
votes
3answers
26k views

Difference between 3NF and BCNF in simple terms (must be able to explain to an 8-year old)

I have read the quote : data depends on the key [1NF], the whole key [2NF] and nothing but the key [3NF]. However, I am having trouble understanding 3.5NF or BCNF as it's called. Here is what I ...

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