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In the attribute dictionary, types and lengths are written like
1 character
10 variable characters
datetime
10 numeric integers
....
Check the slides of Week 6. Conceptual Database Design
Thinking about the worksheets and different terminologies. One thing I did note in the lecture was that it was emphasised that relationships have attributes as well, but my take on this is "Multiplicity". Would that be the correct interpretation fo...
Well if the combination of attributes makes up the primary key, then it would be a composite primary key so you would show it as the key. It just also gets partially used by another table as the foreign key so it would just not be labelled as the for...
What I found missing from the case study is billing or POS (Point of Sale) which would draw data from the different tables to produce a final invoice. All the information is recorded. Do we need to worry about an invoice cash receipt table for inst...
Dr. Nasim, i have a question. The 4th paragraph in the project has a sentence that is unclear-'The details of such representatives are recorded as though they were person clients'.is it trying to say that representatives are a separate table or in th...
hi,i have a question regarding the project.This statement is unclear in the last paragraph 'The details of such representatives are recorded as though they were person clients'.
In the given project
1. can there be relationships between more than one entity?For example;can there be a hired relationship between vehicles and depot? as well as between vehicles and client?Can we infer and add extra relationships on our own?
2.can...
Does a paragraph have to be a relation?
If not, are book(5th paragraph) and hire(4th paragraph) allowed to be designed with the same relationship?
In addition, if there are attributes not mentioned in this paragraph, can I add them myself?
For example
T...
If you're unsure how to write the data types in the dictionary, you can refer to a lab previous database file (such as DreamHomeRental.db or printing.db) and use the ".schema" to review them.
The notation (N x) should indicate an integer with a lengt...
Hi, let's say for a certain entity the primary key could be a combination of some attributes which includes a foreign key. In ERD we are not supposed to note down foreign keys so in this case should I create a surrogate key?
Hi, two questions.
In the attribute dictionary, do we refer to SQLite datatypes (i.e., TEXT, NUMERIC, INTEGER, REAL, BLOB) or more general static-typed SQL data types (INT, CHAR, DATE, etc)?
Secondly, for "(N x) a digit string (integer) of length x", i...
Hi Jieh Chia,
When identifying primary keys, you may encounter a situation where there are no natural primary keys, or the ones available aren't suitable, so you can essentially make a surrogate key (which is what you're suggesting).
A surrogate key is...
Hi, I would like to know if the case study does not mention about a unique identifier for an entity (e.g. Vehicle Make Nominated driver), are we allowed to make a unique identifier ourselves (e.g. Nominated Driver ID, etc.)? Thank you.
No, please do not mention foreign keys in the data dictionaries. Basically what you are going to write in the data dicitionaries will be carried to your ERD.
Cheers
