My situation is:
Table member
id
firstname
lastname
company
address data ( 5 fields )
contact data ( 2 fields )
etc
Table member_profile
member_id
html ( something like <h2>firstname lastname</h2><h3>Company</h3><span>date_registration</span> )
date_activity
chat_status
Table news
id
member_id (fk to member_id in member_profile)
title
...
The idea is that the full profile of the member, when viewed is fetched from the member database, in for instance a news overview, the smaller table which holds the basis display info for a member is joined.
However, i have found the need for more often use for the member info that is not stored in the member_profile table, e.g. firstname, lastname and gender, are nescesary when someone has posted a news item (firstname has posted news titled title.
What would be better to do? Move the fields from the member_profile table to the member table, or move the member fields to the member_profile table and perhaps remove them from the member table? Keep in mind that the member_profile table is joined a lot, and also updated on each login, status update etc.
You have two tables named member so i have the feeling your question isn't formed correctly.
What is the relationship between these tables? It looks like you have 3 tables, all one-to-one. So all you need to do is change (fk to member_id in member_profile) to (fk to id in member).
Now you can join in data from either of the 2 extra tables as you wish, without always having to go through member_profile.
[Edit] Also I assume that member_profile.member_id is a fk to member.id. If not, I believe it should :)
Combine them into one table so you're normalizing the name data then create 2 views which replicate the original two tables would be the easy option
Separating the tables between mostly-static fields and frequently-updated fields will improve write performance. So I would stay with what you're doing. If you cache the information from both tables together in a member object, read performance (and thus joining) is less of an issue.
Related
I know this is probably a stupid question to some but I'm required to have this database in 3NF but know very little about normalisation as our teacher has not covered it. Could someone give me a simple yes or no answer as to whether it is in 3NF and if it is not, suggest any changes. Thanks.
Simple answer No. Google transitive dependencies, or even just Google 3NF?
Why is this the case? Because you have some columns that are dependant on other columns in the same table, where those columns aren't part of the primary key.
For example, in your Customer Table you have Postcode and Town, but there is a relationship between the two, i.e. you couldn't have a Postcode for Paris without also having a Town of Paris. This is very weak transitive dependence, and most databases would have this without considering it bad practice, but I think this is enough to break 3NF.
There's another place where it's a little less clear, but I am pretty sure you break 3NF. In your Payment Table you have Deposit Paid, Total Price, Amount Still To Pay, and Fully Paid. There's an argument that given Total Price and Deposit Paid you could determine Amount Still to Pay. There's a very strong argument that you could always determine Fully Paid from the other three "paid" columns.
You can create Person table with id,title,firstname,lastname
You can add person_id to customerTable and employeeTable. And remove title,firstname,lastname fields from that table.
You can create TownTable with columns id,name and then add town_id to customerTable and emloyeeTable. Remove column town ftom that tables
Create contactInfoTable with columns id, contact_type_id, contact_info
Add contact_info_id column to employeeTable and customerTable. Delete another columns about contact info (phoneNo,email) from that tables.
Create contactType table woth columns id,name. Fill two rows to that table with names phone and email
Create personAddress table with columns id, address, town_id
Add personAddress_id to customerTable, employeeTable tables. Remove address,town from that tables
Create TownTable woth columns id,name
You can create userTable with columns id,employee_id,username
You can create passwordTable with id and user_id
Create user_role table with id, user_id, role_id
Create role_table and add id,name
Also add create_date,end_date (Date ), active(nvarchar2(1) or integer) to all your tables. And in your selects use active=1 condition.
Ok I wasn't entirely sure what to title this question, so here's the situation.
I'm big on data integrity... Meaning as many constraints and rules that I can use I want to use in SQL Server and not rely on the application.
So I have a website that has a business directory, and those businesses can create a post.
So I have two tables like this:
tbl_Business ( BusinessID, Title, etc. )
tbl_Business_Post ( PostID, BusinessID, PostTitle, etc. )
There's a FK relationship for the column BusinessID between the two tables. A post cannot exist in the tbl_Business_Post table without the BusinessID existing in the tbl_Business table.
So pretty standard...
I've recently added classifieds to the site. So now I have two more tables:
tbl_Classified ( ClassifiedID, SellerID, ClassifiedTitle, etc. )
tbl_Classified_Seller ( SellerID, SellerName, etc. )
What I'm wanting to do is take advantage of my tbl_Business_Post table to include classifieds in that as well. Think of its usage like a feed... So the site will show recent posts from businesses and classifieds all in one feed.
Here's where I need guidance.
I was tempted to remove the FK relationship on the tbl_Business_Posts...
I thought about creating another separate Posts table that holds the classifieds posts.
Is there a way to make a conditional FK relationship based on a column? For example, if it's a business posting the BusinessID must exist in the Business table, or if its a classifieds post, the SellerID must exist in the Seller table?
Or should I create a separate table to hold the classifieds posts and UNION both the tables on the query?
You might question why I have a "Posts" table and that's hard to explain... but I do need it for the way the site is organized and how the feed works.
It's just that the posts table is perfect and I wanted to combine all posts and organize them by type (Ie: 'business', 'classified', 'etc.') as there might be more later.
So it comes down to, what's the best way to organize this to sustain data integrity from SSMS?
Thank you for guidance.
======== EDIT =========
Full explanation of tbl_Business_Post
PostID PK
Post_Type int <-- 1-21 is business types, 22 for classified type
BusinessID INT <-- This is the FK currently for the tbl_Business
SiblingID INT <-- This is the ID of the related item they're posting on. So for example, if they post a story about one of their products, this is the ProductID, if it's a service, this is the ServiceID.
Post_Title <-- Depending on the post, this could be a Product title, a service title, etc.
So if I changed the structure so it's as follows:
PostID PK
Post_Type int
BusinessID INT <-- this is populated on insert if it's a business.
SellerID INT <-- This is populated on insert if it's a classified seller
SiblingID INT <-- This is either the classifiedID or ProductID, SeviceID, etc. Depending on post type.
So leaning toward Peter's 1st solution/example... interested in the proper way to create check constraints or triggers on this so that if the type is 1-21, it makes sure BusinessID exists in the Business table, or if it's type 22, make sure the SellerID exists in the seller table.
Even going further with this:
If Post_Type = 22, I should make sure that not only is the Seller in the seller table, but the SiblingID is also the ClassifiedID in the Classified table.
1) There's no way to do this kind of conditional FK you're thinking of. What you need here is basically a FK from tbl_Business_Post which points logically to one of two tables, depending on the value in another column of tbl_Business_Post. This situation is what people encounter quite often. But in a relational DB this is not a very native idea.
So OK, this cannot be enforced with a FK. Instead, you can probably enforce this with a trigger or check constraint on tbl_Business_Post.
2) Alternatively, you can do the below.
Create some table tbl_Basic_Post, put there all columns which pertain to the post itself (e.g. PostTitle) and not to the parent entity which this post record belongs/points to (Business or Classified). Then create two other tables which point via a FK to the tbl_Basic_Post table like e.g.
tbl_Business_Post.Basic_Post_ID (FK)
tbl_Classified_Post.Basic_Post_ID (FK)
Put in these two tables the columns which are Business_Post/Classified_Post-specific
(you see, this is basically inheritable in relational DB terms).
Also, make each of these two tables have FKs to their respective parent tables
tbl_Business and tbl_Classified too. Now these FKs become unconditional (in your sense).
To get business posts you join tbl_Basic_Post and tbl_Business_Post.
To get classified posts you join tbl_Basic_Post and tbl_Classified_Post.
Both approaches have their pros and cons.
Approach 1) is simple, does not lead to the creation of too many tables; but it's not trivial to enforce the data integrity.
Approach 2) does not require anything special to enforce data integrity but leads to the creation of more tables.
I may be total standard here, but I have a table with duplicate values across the records i.e. People and HairColour. What I need to do is create another table which contains all the distinct HairColour values in the Group of Person records.
i.e.
Name HairColour
--------------------
Sam Ginger
Julie Brown
Peter Brown
Caroline Blond
Andrew Blond
My Person feature view needs to list out the distinct HairColours:
HairColour Ginger
HairColour Brown
HairColour Blond
Against each of these Person feature rows I record the Recommended Products.
It is a bit weird from a Relational perspective, but there are reasons. I could build up the Person Feature"View as I add Person records using say an INSTEAD OF INSERT trigger on the View. But it gets messy. An alternative is just to have Person Feature as a View based on a SELECT DISTINCT of the Person table and then link Recommended Products to this. But I have no Primary Key on the Person Feature View since it is a SELECT DISTINCT View. I will not be updating this View. Also one would need to think about how to deal with the Person Recommendation records when a Person Feature record disappeared since since it is not based on a physical table.
Any thoughts on this please?
Edit
I have a table of People with duplicate values for HairColour across a number of records, e.g., more than one person has blond hair. I need to create a table or view that represents a distinct list of "HairColour" records as above. Against each of these "HairColour" records I need link another table called Product Recommendation. The main issue to start with is creating this distinct list of records. Should it be a table or could it be a View based on a SELECT DISTINCT query?
So Person >- HairColour (distinct Table or Distinct View) -< Product Recommendation.
If HairColour needs to be a table then I need to make sure it has the correct records in it every time a Person record is added. Obviously using a View would do this automatically, but I am unsure whether you can can hang another table off a View.
If I understand correctly, you need a table with a primary key that lists the distinct hair colors that are found in a different table.
CREATE TABLE Haircolour(
ID INT IDENTITY(1,1) NOT NULL,
Colour VARCHAR(50) NULL
CONSTRAINT [PK_Haircolour] PRIMARY KEY CLUSTERED (ID ASC))
Then insert your records. If this is querying a table called "Person" it will look like this:
INSERT INTO Haircolour (Colour) SELECT DISTINCT HairColour FROM Person
Does this do what you are looking for?
UPDATE:
Your most recent Edit shows that you are looking for a many-to-many relationship between the Person and ProductRecommendation tables, with the HairColour table functioning as a cross reference table.
As ErikE points out, this is a good opportunity to normalize your data.
Create the HairColour table as described above.
Populate it from whatever source you like, for example the insert statement above.
Modify both the Person and the ProductRecommendation tables to include a HairColourID field, which is an integer foreign key that points to the PK field of the HairColour table.
Update Person.HairColourID to point to the color mentioned in the Person.HairColour column.
Drop the Person.HairColour column.
This involves giving up the ability to put free form new color names into the Person table. Any new colors must now be added to the HairColour table; those are the only colors that are available.
The foreign key constraint enforces the list of available colors. This is a good thing. Referential integrity keeps your data clean and prevents a lot of unexpected errors.
You can now confidently build your ProductRecommendation table on a data structure that will carry some weight.
Are you simply looking for a View of distinct hair colors?
CREATE VIEW YourViewName AS
SELECT DISTINCT HairColour
FROM YourTableName
You can query this view like a table:
SELECT 'HairColour: ' + HairColour
FROM YourViewName
If you are trying to create a new (temp) table, the syntax would look like:
SELECT Name, HairColour
INTO #Temp
FROM YourTableName
GROUP BY Name, HairColour
Here the GROUP BY is doing the same work that a DISTINCT keyword would do in the select list. This will create a temp table with unique combinations of "Name" and "HairColour".
You need to clear up a few things in your post (or in your mind) first:
1) What are the objectives? Forget about tables and views and whatever. Phrase your objectives as an ordinary person would. For example, from what I could gather from your post:
"My objective is to have a list of recommended products based on each person's hair colour."
2) Once you have that, check what data you have. I assume you have a "Persons" table, with the columns "Name" and "HairColour". You check your data and ask yourself: "Do I need any more data to reach my objective?" Based on your post I say yes: you also need a "matching" between hair colours and product ids. This must be provided, or programmed by you. There is no automatic method of saying for example "brown means products X,Y,Z.
3) After you have all the needed data, you can ask: Can I perform a query that will return a close approximation of my objective?
See for example this fiddle:
http://sqlfiddle.com/#!2/fda0d6/1
I have also defined your "Select distinct" view, but I fail to see where it will be used. Your objectives (as defined in your post) do not make this clear. If you provide a thorough list in Recommended_Products_HairColour you do not need a distinct view. The JOIN operation takes care of your "missing colors" (namely "Green" in my example)
4) When you have the query, you can follow up with: Do I need it in a different format? Is this a job for the query or the application? etc. But that's a different question I think.
I am dealing with a table that contains both cars and owners (table CO). I am creating another table to contain attributes for an owner (table OwnerAttributes), that a user can assign to through a GUI. My problem lies in the fact that owners are not unique and since I am using SQL Server I cannot create a foreign key on them. There is an id in the table, but it identifies the car and owner as a whole.
The idea I had to get around this problem is to create a new table (table Owners) that contains distinct owners, and then adding a trigger to table CO that would update the Owners with any changes. I can then use table Owners for my OwnerAttributes table and solve my problem.
The question I want answered is if there is a better way to do this?
I am using a preexisting database, that is heavily used by an old application. The application is hooked up to use the table CO for owners and cars. There also exists several other tables that use the CO table. I wish I could split the table into Owners and Cars, but the company doesn't want me to spend all my time doing it as there are several more features I need to add to the application.
Your thoughts on the Owners table are on the right track! Your problem is because your schema is not normalized. It's the fact you're storing two things (cars, and owners) in one table (your table CO).
You are correct that you should make an Owner table, but you should then remove the Owner information from the CO table entirely, and replace it with a foreign key to the Owners table.
So you want something like this:
CREATE TABLE Owner (
ownerID int not null primary key indentity(1,0),
FirstName varchar(255),
LastName varchar(255),
/* other fields here */
)
GO
CREATE TABLE Car
carID int not null primary key identity(1,0),
ownerID int not null references Owner(ownerID),
/* other fields go here */
GO
/* a convenience, read only view to replace your old CAR OWNER table */
CREATE VIEW Car_Owner AS
SELECT c.*, o.FirstName, o.LastName FROM Car c INNER JOIN Owner o ON c.ownerID = o.ownerID
Now, you have everything properly normalized in SQL. A view has given you back the car_owner as one thing in a pseudo-table.
But the real answer is, normalize your schema. Let SQL do what it does best (relate things to other things). Combining the two things on one table will just lead to more problems like you're encountering downstream.
Hopefully this answer seems helpful and not condescending, which is what I was going for! I have learned the hard way that this approach (normalize everything, let the database do some extra work to retrieve/display/insert it) is the only one that works out in the end.
You should create Owner table, Car table, OwnerCar table(if person can has a few cars). Owner table contains fields, that describe owner(owner properties)
I was wondering how can you display multiple values in a database for example, lets say you have a user who will fill out a form that asks them to type in what types of foods they like for example cookies, candy, apples, bread and so on.
How can I store it in the MySQL database under the same field called food?
How will the field food structure look like?
You may want to read the excellent Wikipedia article on database normalization.
You don't want to store multiple values in a single field. You want to do something like this:
form_responses
id
[whatever other fields your form has]
foods_liked
form_response_id
food_name
Where form_responses is the table containing things that are singular (like a person's name or address, or something where there aren't multiple values). foods_liked.form_response_id is a reference to the form_responses table, so the foods liked by the person who has response number six will have a value of six for the form_response_id field in foods_liked. You'll have one row in that table for each food liked by the person.
Edit: Others have suggested a three-table structure, which is certainly better if you are limiting your users to selecting foods from a predefined list. The three-table structure may be better in the case that you are allowing them the ability to enter their own foods, though if you go that route you'll want to be careful to normalize your input (trim whitespace, fix capitalization, etc.) so you don't end up with duplicate entries in that table.
normally, we do NOT work out like this. try to use a relation table.
Table 1: tbl_food
ID primary key, auto increment
FNAME varchar
Table 2: tbl_user
ID primary key, auto increment
USER varchar
Table 3: tbl_userfood
RID auto increment
USERID int
FOODID int
Use similar format to store your data, instead a chunk of data fitted into a field.
Querying in these tables are easier than parsing the chunk of data too.
Use normalization.
More specifically, create a table called users. Create another called foods. Then link the two tables together with a many-to-many table called users_to_foods referencing each others foreign keys.
One way to do it would be to serialize the food data in your programming language, and then store it in the food field. This would then allow you to query the database, get the serialized food data, and convert it back into a native data structure (probably an array in this case) in your programming language.
The problem with this approach is that you will be storing a lot of the same data over and over, e.g. if a lot of people like cookies, the string "cookies" will be stored over and over. Another problem is searching for everyone who likes one particular food. To do that, you would have to select the food data for each record, unserialize it, and see if the selected food is contained within. This is a very inefficient.
Instead you'll want to create 3 tables: a users table, a foods table, and a join table. The users and foods tables will contain one record for each user and food respectively. The join table will have two fields: user_id and food_id. For every food a user chooses as a favorite, it adds a record to the join table of the user's ID and the food ID.
As an example, to pull all the users who like a particular food with id FOOD_ID, your query would be:
SELECT users.id, users.name
FROM users, join_table
WHERE join_table.food_id = FOOD_ID
AND join_table.user_id = users.id;