Questions tagged as 'modelagem'

Tagged questions
3
answers

Do I need to create a primary key with auto increment?

When I create a table that already has a field with a% index unique , which will be referenced by other tables, I can leave it as primary key? Or is it a good practice to create another field, with auto increment , for this purpose? F...
asked by 14.11.2017 / 13:55
1
answer

Relationship 0..1 in practice

Having the following tables:    request    address    table    Orders can be made at the pizza shop, ie for a table. It may be a delivery (address) or it may be a travel order where it does not belong to anyone. In the SQL of the reque...
asked by 08.01.2016 / 18:39
3
answers

Table Structure / Nomenclature

I am developing a permission system and I have a universe of 9 tables, which form the final permission for the user to use my systems, however, I am in doubt about how to build two of them, that of "inherited" permissions of Systems and Groups,...
asked by 19.11.2014 / 14:33
2
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Surrogate Key and Natural Key

I am studying about data warehouse , but I was confused about the concepts of SK and NK. As I understand in a DW, a natural key would be a foregin key column in the dimension table of the column that is PK referring to the same table in...
asked by 18.02.2018 / 18:30
1
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Could you add a UNIQUE field that accepts nulls?

Can I create a field that accepts nulls and say that it is unique? This my table, the CRM indicates that it is a doctor and not a normal person, it has to be unique, but it has to allow for nulls. This field is also a foreign key in another t...
asked by 05.03.2015 / 19:40
2
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How to implement an interface to guarantee a specific contract?

I need to make an interface implement a list of a certain type: public class ITrade<T> { public int date { get; set; } public double price { get; set; } public double amount { get; set; } public string type { get; set; }...
asked by 01.04.2018 / 20:47
1
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Generate number using identity

Is it possible to generate a number before writing the record to the database? Use field identity of SQL Server 2014. Work with Delphi Berlin.     
asked by 23.08.2017 / 16:19
1
answer

Is it necessary to relate the tables to a database?

I have a little knowledge about the database and I know how to use JOIN for certain SELECT s. I'm setting up a simple DB where I have absolute assurance that one table has no relation to another. Is required? Is there anything in...
asked by 26.09.2018 / 22:10
1
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Speed of table crossing - R

Good evening! I cross two bases in Rstudio, using the merge, but I would like to know if using another way (eg left_join), I get faster, because my tables can get 8 million lines. Thank you.     
asked by 08.06.2018 / 04:06
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answer

What kind of system modeling is this?

I have seen in several places companies that develop commercial systems (usually DELPHI), and these systems are modeled so that they have a "server" I believe you get all the model layer and data access (components such as dataset, connections a...
asked by 01.10.2016 / 23:01