I have a database that has many tables. In this database, there are a subset of tables that store information for similar (but distinct) rows of data, and one table that contains common search attributes that can be applied to each table.
There are 18 columns of searchable variables, and I'm not sure which is the best way to set up the indexes. Do I create a single Index for all the pertinent columns, or one Index for each one?
As u can not use SOLR or similar.
You need to emulate this, using MySQL.
To do so u create one table which u de-normalize all other tables into it. Do notice, this table does not replace the other ones. Consider it like a VIEW.
For a simple example. I have a product, and that product can come in several color codes.
Normalization requires me to have 3 tables. One for product, one for colors (name|code) and one table to link them all.
Denormalize it into one table: product code (pk) |name| color code 1|color name 1| color code 2 | color name 2 ..... No I believe it will be easy for u to decide what to index (really based on the queries you do on that table).
Obviously it isn't optimal, but, you need to play with the toys u have.
Something else to consider, which is very similar, is using star schemas
Related
I'm having conception difficulties to implement something in a database. I have two solutions for a problem, and I was wondering which one is the best.
Problem :
Let's picture a table speciality with 2 fields : speciality_id and speciality_name.
So for example :
1 - Mage
2 - Warrior
3 - Priest
Now, I have a table user with fields such as user_id, name, firstname etc ...
In this table, there is a field called speciality. The speciality stores an integer, corresponding to the speciality_id of the table speciality.
That would be acceptable for users that have only one speciality. I want to improve the model to be able to have multiple specialities for a user.
Here are my two solutions :
Create a table 'solution1' which link the user_id with the speciality_id and remove the speciality field in the user table. So for a user which has 2 specialities, 2 rows will be created in the table 'solution1'.
Change the type of the field speciality in the user table to be able to write down the specialities, separated with commas.
For example 2;3
The problem I got with the second solution is for making foreign keys between my table user and my table specialities, to link them. I may have a bit more difficulties with the PHP in the future too, while wanting to get the specilities for a user (will need to use a parser I guess).
Which solution do you find is the best ?
Thanks.
Absolutely go with your first solution.
Create a third "Many-to-Many" table that allows you to relate a user to multiple specialties. This is the only way to go in your case.
When designing tables, you always want to have each column contain one and only one data element. Think about what querying your second solution would look like. What would you do when you wanted to see all users who had a given specialty?
You might try something like this:
select * from user where specialty like '%2%'
Well, what happens when you have specialties that go to 12? Now "2" matches multiple entities. You could devolve further and try to be tricky, but...you really should just make your data design as normal as possible to avoid all the mess, headache, and errors. Go with Solution 1.
i think the best way is to follow solution1 cause solution2 will end up will lot of complexity later on
Let's imagine we have two categories of publications - movies and books. Is it better to create one MySQL table for all publications or two different tables and unite them every time we show them in the united feed?
EDIT: The structure is little different. it has some common and uncommon data
Assuming both categories got the same attributes,
there is no difference in query performance (According to Multiple Table Select vs. JOIN (performance) )
In that case the solution with one table uses slightly more storage than the two table solution as you need a further column for differentiation (e.g. type).
EDIT
As your structure is different, you should use the two-table-solution as you get NULL fields if you use the one-table-solution.
A bad example for the table Publications:
In the given example you do not need an additional attribute to differentiate the two types because you could determine the type by Pages or Director.
You should avoid NULL values, especially when they are not meant to be filled with data in the future.
I have a table Things and I want to add ownership relations to a table Users. I need to be able to quickly query the owners of a thing and the things a user owns. If I know that there will be at most 50 owners, and the pdf for the number of owners will probably look like this, should I rather
add 50 columns to the Things table, like CoOwner1Id, CoOwner2Id, …, CoOwner50Id, or
should I model this with a Ownerships table which has UserId and ThingId columns, or
would it better to create a table for each thing, for example Thing8321Owners with a row for each owner, or
perhaps a combination of these?
The second choice is the correct one; you should create an intermediate table between the table Things and the table Owners (that contains the details of each owner).
This table should have the thing_id and the owner_id as the primary key.
So finally, you well have 3 tables:
Things (the things details and data)
Owner (the owners details and data)
Ownerships (the assignment of each thing_id to an owner_id)
Because in a relational DB you should not have any redundant data.
You should definitely go with option 2 because what you are trying to model is a many to many relationship. (Many owners can relate to a thing. Many things can relate to an owner.) This is commonly accomplished using what I call a bridging table. (Which exactly what option 2 is.) It is a standard technique in a normalized database.
The other two options are going to give you nightmares trying to query or maintain.
With option 1 you'll need to join the User table to the Thing table on 50 columns to get all of your results. And what happens when you have a really popular thing that 51 people want to own?
Option 3 is even worse. The only way to easily query the data is to use dynamic sql or write a new query each time because you don't know which Thing*Owners table to join on until you know the ID value of the thing you're looking for. Or you're going to need to join the User table to every single Thing*Owners table. Adding a new thing means creating a whole new table. But at least a thing doesn't have a limit on the number of owners it could possibly have.
Now isn't this:
SELECT Users.Name, Things.Name
FROM Users
INNER JOIN Ownership ON Users.UserId=Ownership.UserId
INNER JOIN Things ON Things.ThingId=Ownership.ThingId
much easier than any of those other scenarios?
I have this problem in a table where there are 4 columns which include terms describing the product. I want to make this terms editable (and you can add more) in my app and there are 4 groups of them obviously. I created a table who has all these terms altogether but the product table will have to create 4 relationships with the ID of the terms table.
Is this a good solution?
The main reason I don't want to make 4 different tables for the terms is because there aren't many of them and as the app progresses we might have even more different term groups, thus adding many small tables cluttering the database.
Any suggestion?
Update #1: Here is my current schema http://i.imgur.com/q2a1ldk.png
Have a product table and a terms (product_id, terms_name, terms_description) which will allow you to add as many or as little terms for each product as you want. You just need to retrieve all terms from the terms table with a particular product id.
You could try a mapping table:
apputamenti(id, ...)
term_map (apputamenti_id, term_id)
terms (id, text, type)
So you can add as many terms as you want.
Or if you want to specify the mapping with one more field, change:
term_map (apputamenti_id, term_id, map_type)
so you can use an enum for map_type like enum(tipologia, feedback, target) or whatever your original fields where
I have a typical table, e.g.
id(int) name(varchar) address(varchar) date(datetime)
I also have a table that references validation functions for each one, e.g.
id(int) function(varchar) fail_message(varchar)
1 email Please enter a valid email address
2 required This field can not be left blank
I'd like to be able to associate each column from the first table with one or more of these validators.
The only way I can think of doing this is to stuff the ids into the column names e.g. (column name: email;1;2) and keep track of it through PHP, but that seems very messy.
Is there a good way to do this with relational databases? Would a NoSQL implementation suit this problem better?
Similar to what Dan said, a relatively easy way to implement an association in sql would be to do the following:
id(int) function_id(int) col_name(varchar)
1 1 address
2 1 second_address
3 2 address
4 2 name
And then when you want to do the failure check, use the above table to link the error message to the column name (e.g. 'select function_id from above_table where col_name="address"') and then query the failure table. These tables could subsequently be combined using a view with a join so that a single query would suffice.
Hope this helps.
put this in another table that describes the columns for tables oddly this is very much like extending the table that lists table columns with additional columns
let's say if you extend your example with say localized strings that would mean that the fail_message would become a fail_message_id and the table fail_message would have the columns (id, language, message)