Apologies is this is an incredibly obvious question but I'm new to access and have learned it over the past week through a rather daunting project.
Basically I am in the process of designing a database to track everything the company does: people it knows, things it does, meetings it holds, etc.
I think I've structured it pretty well, but what I would like is an "activity" table. Because the activities are diverse, they are all in multiple tables (events, meetings, enquiries, etc), but they all have a sort of general description field. Is there some way to make a table or form that will pull in all of that data and sort of lay it out as:
Date - Type - Description.
Type would be based on where it came from, so if the meetings table was the source of the information, then it would be typed as meeting.
I realise a simpler way to do this would have been to have an activities table with categories as breaking it up seems easier than combining it, but the number of fields that would mean having on one table made that seem impossible to run.
This seems like something that should be simple, but I'm struggling.
Any thoughts? Thanks in advance!
Related
I'm a little stumped on whether i can make this process of changing addresses easier. I'll explain the situation:
Basically I have three entities, Students, Addresses, StudentsAddresses. Students have many addresses, since they can change alot and rapidly (especially foster kids / homeless kids). So ill be changing them a lot. However based on each address I Want a user to attach (enter it via the UI) the price it would cost to pick that student up via bus service. So my initial thought was, ok, let me attach a column onto my join table 'StudentsAddresses' called 'dailyPrice', this is the cost for each day a student is picked up, and another column called 'adjustmentPrice', which is an additional cost for whatever special circumstance that requires extra work to pick up a student. Is my thinking going to cause me problems the more students I have in the future? Will it get harder to manage?
Another option I thought about, was creating a new Table called Pricing. And another join-type table called StudentsAddressesPricing
StudentsAddressPricing has three columns,
studentId
addressId
pricingId
each field connects the three together. So if i ever needed Students, with their addresses, and the pricing, i would query this table and eager load Students, Addresses, and Pricing. Does this approach seem much cleaner since i've abstracted pricing out a bit? Trying to determine the best way to go about this without having to many headaches in the future incase I wan't to add more attributes pricing related, or address related.
And then I even thought, hey what if pricing is just different for one day? How would I even consider that. Would I need a different kind of entity to handle that? Is doing alot of joins going to hurt my application performance?
Just looking for some insight on how others would do it, and criticism on why im off the ball.
The main question you should ask yourself is: on what does the price depend?
If the price is determined by the address, you might as well add it to addresses. If the price also depends on the student (e.g., depending on their financial situation), it would make sense to put it into studentsaddresses.
In other words: The table where the price is stored should have foreign keys to everything outside the table that determines the price. If that makes it fit into one of the existing tables, keep it there.
Okay, so this problem is stumping me somewhat and I would appreciate some help from someone regarding normalisation (and the end goal of having the ability to search all records at once) if at all possible.
I'm trying to construct a database schema that holds birth, baptism, marriage, death & burial records, as entered from original 1800's documents.
Each record type has unique information that needs to be recorded so as it stands I have a table for each type. Please have a look at the following draft schema;
The obvious data to normalise in the three tables I've used in the example (tbBaptism, tbMarriage, tbBurial) are the location, the church and the source as I have done in that draft schema. Ideally the person would also be normalised into their own table, but with the data I am dealing with, it is not possible to identify all individuals.
Now the problem (if indeed it is actually a problem?) is I feel like there must be a better way of storing the data in the tables tbBaptism, tbMarriage, tbBurial ... perhaps combining them into one table? ... possibly an event table which has the common fields such as the event date, location, church, etc. but how would I store the unique fields such as marriage witnesses for example?
Am I trying to over simplify things and is the current draft schema is the way to go?
I'm looking for ideas/suggestions that will make my life easier in the long run!!
Apologies if this is redundant, and it probably is, I gave it a look but couldn't find a question here that fell in with what I wanted to know.
Basically we have a table with about ~50000 rows, and it's expected to grow much bigger than that. We need to be able to allow admin users to add in custom data to an item based on its category, and users can just pick which fields defined by the administrators they want to add info to.
Initially I had gone with an item_categories_fields table which pairs up entries from item_fields to item_categories, so admins can add custom fields and reuse them across categories for consistency. item_fields has a relationship to item_field_values which links values with fields, which is how we handled things in .NET. The project is using CAKEPHP though, and we're just learning as we go, so it can get a bit annoying at times.
I'm however thinking of maybe just adding an item_custom_fields table that is essentially the item_id and a text field that stores XMLish formatted data. This is just for the values of the custom fields.
No problems if I want to fetch the item by its id as the required data is stored in the items table, but what if I wanted to do a search based on a custom field? Would a
SELECT * FROM item_custom_fields
WHERE custom_data LIKE '%<material>Plastic</material>%'
(user input related issues aside) be practical if I wanted to fetch items made of plastic in this case? Like how slow would that be?
Thanks.
Edit: I was afraid of that as realistically this thing will be around 400k rows for that one table at launch, thanks guys.
Any LIKE query that starts with % will not use any indexes you have on the column, so the query will scan the whole table to find the result.
The response time for that depends highly on your machine and the size of the table, but it definitely won't be efficient in any shape or form.
Your previous/existing solution (if well indexed) should be quite a bit faster.
I am making a database that is for employee scheduling. I am, for the first time ever, making a relational mySQL database so that I can efficiently manage all of the data. I have been using the mySQL Workbench program to help me visualize how this is going to go. Here is what I have so far:
What I have pictured in my head is that, based on the drawing, I would set the schedule in the schedule table which uses references from the other tables as shown. Then when I need to display this schedule, I would pull everything from the schedule table. Whenever I've worked with a database in the past, it hasn't been of the normalized type, so I would just enter the data into one table and then pull the data out from that one table. Now that I'm tackling a much larger project I am sure that having all of the tables split (normalized) like this is the way to go, but I'm having trouble seeing how everything comes together in the end. I have a feeling it doesn't work the way I have it pictured, #grossvogel pointed out what I believe to be something critical to making this all work and that is to use the join function to pull the data.
The reason I started with a relational database was so that if I made a change to (for example) the shift table and instead of record 1 being "AM" I wanted it to be "Morning", it would then automatically change the relevant sections through the cascade option.
The reason I'm posting this here is because I am hoping someone can help fill in the blanks and to point me in the right direction so I don't spend a lot of hours only to find out I made a wrong turn at the beginning.
Maybe the piece you're missing is the idea of using a query with joins to pull in data from multiple tables. For instance (just incorporating a couple of your tables):
SELECT Dept_Name, Emp_Name, Stat_Name ...
FROM schedule
INNER JOIN departments on schedule.Dept_ID = departments.Dept_ID
INNER JOIN employees on schedule.Emp_ID = employees.Emp_ID
INNER JOIN status on schedule.Stat_ID = status.Stat_ID
...
where ....
Note also that a schedule table that contains all of the information needed to be displayed on the final page is not in the spirit of relational data modeling. You want each table to model some entity in your application, so it might be more appropriate to rename schedule to something like shifts if each row represents a shift. (I usually use singular names for tables, but there are multiple perspectives there.)
This is, frankly, a very difficult question to answer because you could get a million different answers, each with their own merits. I'd suggest you take a look at these (there are probably better links out there too, these just seemed like good points to note) :
http://www.devshed.com/c/a/MySQL/Designing-a-MySQL-Database-Tips-and-Techniques/
http://en.wikipedia.org/wiki/Boyce%E2%80%93Codd_normal_form
http://www.sitepoint.com/forums/showthread.php?66342-SQL-and-RDBMS-Database-Design-DO-s-and-DON-Ts
I'd also suggest you try explaining what it is you want to achieve in more detail rather than just post the table structure and let us try to figure out what you meant by what you've done.
Often by trying to explain something verbally you may come to the realisations you need without anyone else's input at all!
One thing I will mention is that you don't have to denormalise a table to report certain values together, you should be considering views for that kind of thing...
I have my own theories on the best way to do this, but I think its a common topic and I'd be interested in the different methods people use. Here goes
Whats the best way to deal with many-to-many join tables, particularly as far as naming them goes, what to do when you need to add extra information to the relationship, and what to do whene there are multiple relationships between two tables?
Lets say you have two tables, Users and Events and need to store the attendees. So you create EventAttendees table. Then a requirement comes up to store the organisers. Should you
create an EventOrganisers table, so each new relationship is modelled with a join table
or
rename EventAttendees to UserEventRelationship (or some other name, like User2Event or UserEventMap or UserToEvent), and an IsAttending column and a IsOrganiser column i.e. You have a single table which you store all relationship info between two attendees
or
a bit of both (really?)
or
something else entirely?
Thoughts?
The easy answer to a generic question like this is, as always, "It all depends on the details".
But in general, I try to create fewer tables when this can be done without abusing the data definitions unduly. So in your example, I would probably add an isOrganizer column to the table, or maybe an attendeeType to allow for easy future expansion from audience/organizer to audience/organizer/speaker/caterer or whatever may be needed. Creating an extra table with essentially identical columns, where the table name is in effect a flag identifying the "attendee type", seems to me the wrong way to go both from a pristine design perspective and also from a practical point of view.
A single table is more flexible. With one table and a type field, if we want to know just the organizers -- like when we're sending invitations to a planning meaning -- fine, we write "select userid from userevent where eventid=? and attendeetype='O'". If we want to know everyone who will be there -- like when we're printing name cards for the lunch tables -- we just don't include the attendeetype test.
But suppose we have two tables. Then if we want just the organizers, okay, that's easy, join on the organizer table. But if we want both organizers and audience, then we have to do a union, which makes for more complicated queries and is usually slow. And if you're thinking, What's the big deal doing a union?, note that there may be more to the query. Perhaps a person can have multiple phone numbers and we care about this, so the query is not just joining user and eventAttendee but also phone. Maybe we want to know if they've attended previous conferences because we give special deals to "alumni", so we have to join in eventAttendee a second time, etc etc. A ten-table join with a union can get very messy and confusing to read.