441 reputation
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bio website damirsystems.com/?page_id=5
location Toronto, Canada
age 53
visits member for 2 years, 1 month
seen 20 hours ago

May
15
comment Rules for Decomposition to 2 NF
Simple, you do not stop before BCNF -- why would you?
May
15
comment Rules for Decomposition to 2 NF
If the table is in 3NF then it is also in 2NF and 1NF. Your decomposition algorithm should take you to BCNF.
Apr
22
comment How to convert this relation to 2NF?
... [cont] And if the rule states that all clases do have the same duration, and that can not change, then you can simply drop the CEndTime column.
Apr
22
comment How to convert this relation to 2NF?
No, the partial dependency does not exists -- you are interpreting your current data where all classes have the same duration; however, given that a class may have any duration that conclusion is not valid. When defining FD you must focus on the business rule and all possible legal data values, not the current set of values.
Apr
7
comment Does redundancy exists in this table?
@Jose_Sunstrider; well still flawed; left a comment on the article there.
Apr
6
comment Does redundancy exists in this table?
Where did you find that definition? It is flawed -- think UserID appearing in multiple tables.
Oct
31
comment If all variables are a subset of the candidate key, is the database design 5NF?
@Lukazoid -- study that link before providing data and rules. That example contains a table and dataset that can be considered BCNF or 6NF just by stating a business rule -- same table same data.
Oct
9
comment Two possibilities of primary key
@RafaelBarros; here on DBA.SE site.
Oct
9
comment Two possibilities of primary key
Your question is really confusing. Are you saying that there are two types of users? If so, which columns are common and which are specific to each type? Or, do both types have id_1 and id_2?
Oct
9
comment Database design question
Many gigabytes? So, if you buy a 1TB blade it all fits into memory? Why would you prefer distributed file system over in-memory DB?
Mar
15
comment What alternatives exist when a table requires too many foreign keys?
Could you provide schema example for say 5 of these tables ...
Mar
10
comment Simple scenario needs to go from Unnormalized Data to 3NF - Review Please
.. (cont) So to summarize, if "normalizing" using decomposition, you should include enough examples to expose all FDs and JDs. The other way is not to use normalization at all, but to apply a design process which leads to (usually) 5NF directly, as a result of the process itself. But your question is very specific, so I'll skip on that one.
Mar
10
comment Simple scenario needs to go from Unnormalized Data to 3NF - Review Please
If you just blindly follow rules on this table, you will get stuck. For example, this table has FD {ID} --> {Name}, but also {Name} --> {ID}, and {Name} --> {Supplier}. Is this correct considering the business? Add more data to include more records of dog (cat) food ...; and possibly bought from different suppliers. As you add data, FD {ID} --> {Name} will disappear, probably same for FD {Name} --> {Supplier}; but some more may pop up probably MVD or JD regarding supplier and product. ..
Mar
4
comment UML class diagramm for database design?
sparxsystems.com/resources/uml_datamodel.html
Sep
25
comment Economic Database Architecture Possibilities w/ Data of Varying Length
@idubs11; they can run it on analytic tables, that's OK, but not on the temporal structure above. Well they can, but advanced users only. The thing is that any 5NF views would get bogged down due to lack of "table elimination" in optimizer, so users would have to properly pick all tables they need for each query ....
Sep
18
comment How do I optimize this database design?
Also User_Cars and Vehicles_Hardware, both FKs should be part of a PK, -- the way it is now, both tables allow duplicate entries.
Sep
18
comment How do I optimize this database design?
Tracking must point to Vehicles_Hardware FK {vehicle_number, hardware_id}. The way it is now, it allows for any combination of vehicle_number, hardware_id even if they are not paired together.
Sep
7
comment SQL Server - Database per company. How to query across databases?
And your client is aware that there can be no foreign keys (referential integrity) across DBs?
Jul
15
comment Database tables design
@JNK; I strongly disagree with force-moving away from SO; see meta.stackexchange.com/questions/109749/…
Jul
15
comment Database tables design
@Ben, did you ask for this question to be moved form SO here?