506 reputation
36
bio website damirsystems.com/?page_id=5
location Toronto, Canada
age 53
visits member for 2 years, 4 months
seen 7 hours ago

Sep
25
answered Architecting table with multiple paths to common parent tables
Aug
15
answered Should I add transitive foreign keys?
Aug
13
comment Identifying functional dependencies
If {A} -> {C} holds, then {A,+} -> {C} holds too. IF {C} -> {A} holds then {C,+} -> A holds too; therefore {C,D} -> {A} is true. Same logic for {B,C} -> E and {B,C,A} -> E. Not sure which book you have, but there are many bad DB books out there... in other words throw this one to garbage and get some classics.
Jun
24
awarded  Yearling
May
16
answered Rules for Decomposition to 2 NF
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
17
revised Advanced design question related to compound primary keys
added 11 characters in body
Apr
17
revised Advanced design question related to compound primary keys
added 7 characters in body
Apr
17
answered Advanced design question related to compound primary keys
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
31
revised If all variables are a subset of the candidate key, is the database design 5NF?
added 25 characters in body
Oct
31
answered If all variables are a subset of the candidate key, is the database design 5NF?
Oct
9
comment Two possibilities of primary key
@RafaelBarros; here on DBA.SE site.
Oct
9
answered Two possibilities of primary key
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?