Handling multi-select list in database design - sql-server

I'm creating a clinic management system where I need to store Medical History for a patient. The user can select multiple history conditions for a single patient, however, each clinic has its own fixed set of Medical History fields.
For example:
Clinic 1:
DiseaseOne
DiseaseTwo
DiseaseThree
Clinic 2:
DiseaseFour
DiseaseFive
DiseaseSize
For my Patient visit in a specific Clinic , the user should be able to check 1 or more Diseases for the patient's medical history based on the clinic type.
I thought of two ways of storing the Medical History data:
First Option:
Add the fields to the corresponding clinic Patient Visit Record:
PatientClinic1VisitRecord:
PatientClinic1VisitRecordId
VisitDate
MedHist_DiseaseOne
MedHist_DiseaseTwo
MedHist_DisearThree
And fill up each MedHist field with the value "True/False" based on the user input.
Second Option:
Have a single MedicalHistory Table that holds all Clinics Medical History detail as well as another table to hold the Patient's medical history in its corresponding visit.
MedicalHistory
ClinicId
MedicalHistoryFieldId
MedicalHistoryFieldName
MedicalHistoryPatientClinicVisit
VisitId
MedicalHistoryFieldId
MedicalHistoryFieldValue
I'm not sure if these approaches are good practices, is a third approach that could be better to use ?

If you only interested on the diseases the person had, then storing the false / non-existing diseases is quite pointless. Not really knowing all the details doesn't help getting the best solution, but I would probably create something like this:
Person:
PersonID
Name
Address
Clinic:
ClinicID
Name
Address
Disease:
DiseaseID
Name
MedicalHistory:
HistoryID (identity, primary key)
PersonID
ClinicID
VisitDate (either date or datetime2 field depending what you need)
DiseaseID
Details, Notes etc
I created this table because my assumption was that people have most likely only 1 disease on 1 visit, so in case there's sometimes several, more rows can be added, instead of creating separate table for the visit, which makes queries most complex.
If you need to track also situation where a disease was checked but result was negative, then new status field is needed for the history table.
If you need to limit which diseases can be entered by which clinic, you'll need separate table for that too.

Create a set of relational tables to get a robust and flexible system, enabling the clinics to add an arbitrary number of diseases, patients, and visits. Also, constructing queries for various group-by criteria will become easier for you.
Build a set of 4 tables plus a Many-to-Many (M2M) "linking" table as given below. The first 3 tables will be less-frequently updated tables. On each visit of a patient to a clinic, add 1 row to the [Visits] table, containing the full detail of the visit EXCEPT disease information. Add 1 row to the M2M [MedicalHistory] table for EACH disease for which the patient will be consulting on that visit.
On a side note - consider using Table-Valued Parameters for passing a number of rows (1 row per disease being consulted) from your front-end program to the SQL Server stored procedure.
Table [Clinics]
ClinicId Primary Key
ClinicName
-more columns -
Table [Diseases]
DiseaseId Primary Key
ClinicId Foreign Key into the [Clinics] table
DiseaseName
- more columns -
Table [Patients]
PatientId Primary Key
ClinicId Foreign Key into the [Clinics] table
PatientName
-more columns -
Table [Visits]
VisitId Primary Key
VisitDate
DoctorId Foreign Key into another table called [Doctor]
BillingAmount
- more columns -
And finally the M2M table: [MedicalHistory]. (Important - All the FK fields should be combined together to form the PK of this table.)
ClinicId Foreign Key into the [Clinics] table
DiseaseId Foreign Key into the [Diseases] table
PatientId Foreign Key into the [Patients] table
VisitId Foreign Key into the [Visits] table

Related

Elimination of cycle between relationships in the proposed ER diagram

In making an ER schema for a simple database, I have encountered the following problem:
I get a cycle in the diagram, which I don't know if it is redundant or I could eliminate it somehow.
I present the problem on a large scale:
The visit entity records visits to London by a vehicle. This entity contains information on their arrival, departure and total visit time.
The vehicle entity contains information on the vehicle's place of origin, CO2 emissions and its number plate.
The entity date contains information for each date of the day of the week to which it corresponds and the name of the holiday for any region added.
The region of the entity Date is matched to the Vehicle region. The entry_date/end_date of the entity Visit is matched to the date of the entity Date. Finally, the number plate of the entity Vehicle is matched to the number plate of the entity Visit. In this way, the cycle that I mentioned at the beginning appears.
The ER diagram is as follows:
If there are any questions about the problem that I have not explained, please do not hesitate to ask me. I welcome suggestions for improving the ER diagram, either to remove the cycle or to simply keep it as it is if you think it is correct.
My two cents -
"Date" is really not a good name for entity or table.
First, it is too general to convey what you really refer to.
Second, it is a reserved key word in most common languages. You just cause unnecessary trouble for programming.
You use "Date" to get holiday name (for particular region) and week day, right?
My suggestion is that you only need to save holidays in this table because weekday can be figured out in most common programming language.
This "Date" table is just a lookup table to help you find out holiday, you do not need to enforce relation between "Date" and Visit
I'd also suggest you add Region table to enforce consistent naming.
Here is the DB diagram, I renamed "date" to "holiday"
Here is the SQL server implementation -
create table region (
region_code varchar(100) primary key
,region_name varchar(100)
)
create table holiday (
holiday_date date not null
,region_code varchar(100) not null
,holiday_name varchar(100) not null
)
alter table holiday add primary key (holiday_date, region_code)
alter table holiday add foreign key (region_code) references region (region_code)
create table vehicle (
number_plate varchar(100) primary key
,region_code varchar(100) not null
,CO2_emission varchar(100)
)
alter table vehicle add foreign key (region_code) references region (region_code)
create table visit (
number_plate varchar(100) not null
,entry_date date not null
,end_date date
)
alter table visit add primary key (number_plate, entry_date)
alter table visit add foreign key (number_plate) references vehicle (number_plate)
The Relate relationship between Vehicle and Date entity is redundant here. You can still find the dates for each visit a vehicle completed from the existing relationships. If you convert the ER diagram to DB tables, it'll be more clear.
Why are entry_date and exit_date two attributes of the Visit entity? These are already considered by the many-to-2 relationship with the Date entity. Remove these two attributes along with number_plate from Visit. Lastly, add an unique id to the Visit entity.

Access Relationship Design

I am fairly green when it comes to working with Access and databases in general.
I am asking for your help in figuring out how to set the correct relationships for three tables:
Table 1 contains:
(no unique ID)
SalesTripID
EmployeeName
StartDate
EndDate
*Each record on this table is related to 1 specific employee's 1 specific sales trip
Table 2 contains:
HotelName
HotelStart
HotelEnd
HotelTotal
*This table may contain multiple records that belong to only 1 record on table 1 (for instance, an employee would stay at 2 hotels during their sales trip)
Table 3 contains:
(no unique ID)
MealVendor
MealDate
MealTotal
*This table, similar to Table 2, may have multiple records in it that are tied to the 1 SalesTripID
How do I set something up to show me each SalesTripID, the multiple Table 2, and the multiple Table 3 records associated with it? Do I need to add a Primary Key anything other than Table 1? Is writing a query involved to display the information? Because I am so green, any and all feedback is welcome.
The following is my recommendation:
Add a SalesTripId field on tables 2,3. This is called a ForeignKey.
If SalesTripId in Table1 is not unique (i.e. each employee can have a trip with the same Id as another employee), add another field (Id) in Table1. You can use Access' AutoNumber type for that field.
I recommend always having a primary key in your tables. But you can skip the Id fields in tables 2,3.

Microsoft Access 2013 - Multiple Foreign Keys in the same Record

I’ve encountered a problem with pulling multiple foreign keys into one record in a Microsoft Access table.
I’ve got two tables with these fields:
Table 1:
Owners
Fields:
Owner ID (Primary Key)
First Name
Last Name
Table 2:
Ships
Fields:
Ship ID (Primary Key)
Ship Name
I need to create a relationship between Table 1 and Table 2 which shows who owns the ship. I’ve tried adding a number field to Table 2 called Owner ID (Foreign Key) and this works absolutely fine.
Working Example:
Table 1 – Owners Table 2 – Ships
Owner ID (Primary Key)__ Ship ID (Primary Key)
First Name \ Ship Name
Last Name \________Owner ID (Foreign Key)
Unfortunately my ships in Table 2 can have multiple owners (up to 5) at the same time. My problem arises when I try to create a series of linking fields in Table 2.
Not Working:
Table 1 – Owners Table 2 – Ships
Owner ID (Primary Key)__ Ship ID (Primary Key)
First Name \ Ship Name
Last Name \ Owner1 ID (Foreign Key)
\______/ Owner2 ID (Foreign Key)
\ Owner3 ID (Foreign Key)
Can anyone recommend any workarounds so I can show multiple owners taken from the Owners table in the Ships table?
Thanks for your help!
Your database design is definitely incorrect.
In the case you explain, you have a many-to-many relationship between Ships and Owners, which MUST translate into a "relationship table" in the relational model.
In this case: a [Ownership] table, with 2 fields, being the 2 Primary Keys (PK) of the related tables.
In other words, you need 3 tables:
Ships(ShipId, ShipName, Whatever) PK is ShipId
Owner(OwnerId, FirstName, LastName) PK is OwnerId
OwnerShip(ShipId, OwnerId) PK is made of the 2 FKs
The problem is that it looks like Access doesn't allow Nullable FK's and so all Owner fields would have to be filled in, no matter how many owners there are.
The only solution to this I can think of is to introduce a ShipOwner table, which has ShipID and OwnerID columns (as FK's to the Ship and Owner tables). You can then have as many Owners as you like.
Pros: You can add things like %Owned if that matters
Cons: The software has to enforce the limit of 5 owners
Biggest Pro: it will work!
Cheers -
EDIT: The first para is wrong: Access does let you add nullable FK's. However I still thing the suggestion here is a good one. Repeating Groups (Owner 1 to 5) is against Normalisation rules, and this suggestion is normalised.

Change ID of row and reflect this change to all related tables

Old version
I have a Person table and the table Company.
both tables have a column Id (Identity)
Table Company have Ids of 1 to 165
In the table Person have Ids 1 until 2029
New Version
In the new version of the system, was created a table Entity.
This table contains the records of the Companies and People
The Company and Person tables will be maintained, referring to the Entity table.
The Id in table Entity will be the same in Company or Person table
Question
Both tables have multiple relationships with other tables.
Table Entity (as well as others) has a column ID (identity).
The problem is that the Id were repeated when the two tables together (It was to be expected).
How to import without losing relationships?
Attempts
I thought of changing the value of Ids in Company table, starts from 2030.
Thus the Ids would not duplicate when joining the two tables.
But this creates another questions.
How to do this without losing existing relationships?
How to change the Id of a row in the table and this is reflected in all tables which it relates?
I would like to do this using only DDL (SQL Server)
I thought of changing the value of Ids in Company table, starts from 2030. Thus the Ids would not duplicate when joining the two tables.
Create foreign key constraints on the Person table to all related tables (or alter the existing foreign key constraints) with ON UPDATE CASCADE. Then update the Person table and change the values if the id columns - these changes will cascade to the related tables.
To stop further problems, maybe change the identity columns in Person and Company to something like identity( 1000, 3 ) and identity (1001, 3) respectively.
However, I think the best idea is to have a different EntityID column in the Entity table, unrelated to PersonID and CompanyID. The Entity table would also have a column called AltEntityID or BusinessKey that contains the id from the other table and that does not have a unique constraint or a foreign key constraint.
And if you make small modification to your attempt - add new column, say newId, to Company and to Person to manage relation with Entity and leave id columns as is. Why this is the simpliest way? Because new columns shouldnot be identity columns, from one side. From the other side, you can leave all logic of relating other tables with Company and Person intact.

SQL Server table PK and FK

I am creating a relationship between 2 tables:
The relationship I like to form is between the Inventory an InventoryExtended tables.
The primary key for the Inventory table is InvID (Inventory ID).
The reason why I created the InventoryExtended is becauses only 1% of the inventory items in the Inventory table will need additional or extended fields, the rest will not.
Instead of adding these additional fields in the Inventory table where 99% will be blank for 50 additional fields that I need I decided to create an InventoryExtended table and store the 50 fields there.
The relationship between the Inventory an InventoryExtended table will be 1 to 1.
Meaning, for the 1% of the records in the Inventory table , the InvId will be the same as the InvId in the InventoryExtended table.
My question is that should the InvID in the InventoryExtended table be a FK (Foreign Key) or should it be a PK and a FK?
I am thinking it should be a PK and a FK as there the InvID will be unique in the InventoryExtended table.
Thanks in advance.
You are correct.
The InvID should be a PRIMARY KEY and a FOREIGN KEY as it will be unique in the InventoryExtended table.
This type of relationship is indeed 1:1 or (more accurately) 1::0..1, as only some of the rows in the Inventory table will have a related row in InventoryExtended.
Also note that the InventoryExtended (InvID) should not have the IDENTITY property, even if the Inventory (InvID) has it.
The InvID will be both a PK and FK for the extended table.
If you know in advance (meaning when you attempt to fetch data) whether or not a particular inventory type will have the extended data, for such records you can even skip the original table altogether and simply use two disjoint tables smallInventory and bigInventory such that no records of one are present in the other.

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