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I have 3 tables
Table1: Plant Table
PlantId(Primary key)
Plantname
and some other fields
Table2 :Inputfiles
Plantname,Filename
PlantId(foreign key) references PlantId(Plant)
Table 3; InputData
Id.
and other fields
I need to design it such a way that one plant can have many inpufiles So this is a 1-m between Plant Table and Inputfiles tables
Now when the user selects a inputfile from table2, all the data related to the input file is stored in Inputdata table3.
What should be the relation between table2(input files) and table3(inputdata)
Thank you
sun
A 1-1 relationship should exist between inputfiles and inputdata.
Based on your description of the problem, I would have inputfiles have the inputdata.id as a foreign key.
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when we have two tables, suppose A and B,there exists one to many relationship between these two, than can there be element from A that are not connected to any element from B?
One to many relationship between relational tables is a concept that primarily means that if there is a record in table A, then it can have many associated records in table B.
For e.g. customer_id record in table A can have many loans for that customer in table B.
So 1 customer_id associated with many loan_ids in another table.
Coming back to your question, it is possible that 1 loan_id in loan_table can have multiple guarantors in guarantor_table and it is also possible that a loan does not have a guarantor associated with it. So even though there is one to many relationship between the tables it does not mean it will always have many records in table B for one record in table A.
Check this link - What is the difference of partiality and optionality when drawing ER diagrams
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I have a couple of properties in my sql server SLS.Customer table which are references to other tables. I can't think of proper names for those tables. Help please :)
Table1: Contains the "How did you hear about us" values. (Example records: Through a friend, Advertisement, Seminar x, conference y, etc.)
Table2: Contains various reasons a customer refused to buy our product.
Table3: Contains the industry/business type a customer belongs to. (I thought of CustomerIndustry or just Industry but it sounds strange!!
Table4: Contains contact info of the person(s) related to a customer entity (specially if the customer is a company, rather than an individual, I need contact info of a person in charge). This is different from the tables PartyAddress and PartyPhones
As the question is suggestion based. I just put some suggestions here.
Table1:
RefererInfo
RefererDetails
Table2:
backlogReasons
backlogInfo
backlogDetails
Table3:
CustomerCategory
CustomerBackground
Table5:
PersonInChargeForParty
ContactsForParty
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I am having trouble creating a report by pulling information from my database using sql-server. I have 3 tables: Incident, Action and Agency.
Within the Incident table I have attributes such as a
primary key (incident_id)
and others (status and action_id).
In my Action table I have the
foreign keys (incident_id and agency_id)
a primary key (action_id).
In my
Agency table
I have a
primary key (agency_id)
and other attributes such as (agency_name and agency_type).
I need an sql statement that groups according to type, sums the number of actions an incident has and orders them from highest to lowest, where the status is closed.
Any help would be greatly appreciated.
Thanks for your time.
Using MySQL syntax, the following should help get you along the way:
SELECT ag.agency_type, count(ac.action_id)
FROM
incident AS i INNER JOIN
action AS ac ON i.incident_id=ac.incident_id INNER JOIN
agency AS ag ON ac.agency_id=ag.agency_id
WHERE i.status='Closed'
GROUP BY ag.agency_type
ORDER BY count(ac.action_id) DESC;
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I have the following entities in my system: COMPANY, POSITION, APPLICANTS. There is many to many relationships between POSITION and APPLICANTS, but the current model does not show that there is many to many relationships between COMPANY and APPLICANTS.
Does it make sense to you to have a join table foo that has the company_id, position_id and applicant_id or i should have a table that joins COMPANY and POSITION and another that joins POSITION and APPLICANTS?
I don't think so. You can get APPLICANT for a given COMPANY via JOIN with POSITION.
I think a relationship between a COMPANY and an individual becomes significant when they shift from APPLICANT to EMPLOYEE. I would not model it as you propose.
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I have 2 tables User and User_Event
User
id PK BIGINT
User_Event
event_id PK BIGINT
user_id FK References User.id
Should I create above tables before runtime
OR
should I create table "User_Event" for each Existing user at runtime (In this case table name would be like this
User_Event_user001,User_Event_user002....)
Now my questions is
1. Which design is better?
2. which implementation is faster?
For both questions, the best answer is to have an invariant database structure.
Modifying/creating the tables is a lot of work for databases, as they are designed for managing DATA inside the defined structures (tables, views).
It is very rare that changing the structure on the fly is pertinent, and even less effective.
--> create tables before runtime !
I don't know what is purpose of your system but classical implementation is to have one table User_Event and store data about all users in this table. If you want to get info for one user you should use query:
SELECT event_id FROM User_Event where user_id=<your user_id>;