The relationship between these tables appears to be many sessions with 1 trainer,
but it should be 1 session has many trainers. 1
Have I just misunderstood something? Why does access not use the same notation as an ERD? 2
.. it should be 1 session has many trainers.
Then you must have a subtable to hold a record for each trainer assigned a session.
For example, four records with the same SessionId and four TrainerIds.
Same goes for participiants.
Related
I have two tables, one user table and an items table. In the user table, there is the field "items". The "items" table only consists of a unique id and an item_name.
Now each user can have multiple items. I wanted to avoid creating a third table that would connect the items with the user but rather have a field in the user_table that stores the item ids connected to the user in a "csv" field.
So any given user would have a field "items" that could have a value like "32,3,98,56".
It maybe is worth mentioning that the maximum number of items per user is rather limited (<5).
The question: Is this approach generally a bad idea compared to having a third table that contains user->item pairs?
Wouldn't a third table create quite an overhead when you want to find all items of a user (I would have to iterate through all elements returned by MySQL individually).
You don't want to store the value in the comma separated form.
Consider the case when you decide to join this column with some other table.
Consider you have,
x items
1 1, 2, 3
1 1, 4
2 1
and you want to find distinct values for each x i.e.:
x items
1 1, 2, 3, 4
2 1
or may be want to check if it has 3 in it
or may be want to convert them into separate rows:
x items
1 1
1 2
1 3
1 1
1 4
2 1
It will be a HUGE PAIN.
Use atleast normalization 1st principle - have separate row for each value.
Now, say originally you had this as you table:
x item
1 1
1 2
1 3
1 1
1 4
2 1
You can easily convert it into csv values:
select x, group_concat(item order by item) items
from t
group by x
If you want to search if x = 1 has item 3. Easy.
select * from t where x = 1 and item = 3
which in earlier case would use horrible find_in_set:
select * from t where x = 1 and find_in_set(3, items);
If you think you can use like with CSV values to search, then first like %x% can't use indexes. Second, it will produce wrong results.
Say you want check if item ab is present and you do %ab% it will return rows with abc abcd abcde .... .
If you have many users and items, then I'd suggest create separate table users with an PK userid, another items with PK itemid and lastly a mapping table user_item having userid, itemid columns.
If you know you'll just need to store and retrieve these values and not do any operation on it such as join, search, distinct, conversion to separate rows etc. etc. - may be just may be, you can (I still wouldn't).
Storing complex data directly in a relational database is a nonstandard use of a relational database. Normally they are designed for normalized data.
There are extensions which vary according to the brand of software which may help. Or you can normalize your CSV file into properly designed table(s). It depends on lots of things. Talk to your enterprise data architect in this case.
Whether it's a bad idea depends on your business needs. I can't assess your business needs from way out here on the internet. Talk to your product manager in this case.
i want to log all payment transactions. but i cant decide if i should store the id leading to the value or directly the value itself. if i store the id's of values then i have to store the values as long as the log exists. but if i store the values alone then i could have problems on tracking the informations. which way do you think could be more healty?
ACCOUNT TABLE
id title
0 Color Inc
1 Farbe Gmbh
USER TABLE
id name surname
1 joe zimmermann
2 hans black
LOG TABLE
id user_id account_id amount
0 1 0 330
1 2 1 10
in this example above i store the id's of the values.
LOG TABLE
id user_name account_title amount
0 joe Color Inc 330
1 hans Farbe Gmbh 10
Here i logged the values directly. So what do you think?
In case of transactions (like a virtual pos terminal on a web page), I find it better to log everything I can. For example: Timestamp, direction, amount, type of transaction, partnerid, id of the invoice or other certificate which connected to the transaction.
These kind of stuff, where you can't make any mistake, or if you do, you have to be able to trace back everything. So I recommend saving a reasonable amount of data for each and every transactions.
I would like a table or query in mysql of all permutations of two separate datasets, but with rules.
I have a table of jobs, and a table of drivers.
I'd like to produce table or query of all combinations of jobs to drivers. Each job must have a driver, but each driver doesn't necessarily need a job. Like this:
In this example I have 4 jobs and 3 drivers.
Job1 | Job2 | Job3 | Job4
1 1 1 1
1 1 1 2
1 1 1 3
1 1 2 1
1 1 3 1
This, I can't do, so if someone could help me that would be awesome. I believe that the number of rows in this example would be 4 to the power 3 (jobs to the power of drivers) which is 64 rows.
But the second part of this is what I call the "rules". Each job will have defined drivers that can do the job.
For example Job 1 can only be done by driver 1 or 3.
Job 2 can only be done by driver 1.
etc
I was thinking that if I did a create table, then running delete queries, but I am really at a loss. I would like to just create the query using the rules to start with in an attempt to speed it up.
This will eventually help me to make a plan for each job by showing all the ways that these jobs can be assigned.
Sorry for being vague but I'm hoping the community can help me out here.
Edit:
I think my maths may have been wrong. According to this: combination calculator where I input 3 to choose from (drivers) and 4 numbers chosen (jobs) order is important and repetition is allowed (not sure what that is) then it produces 81.
Although way unclear and smells like homework, her my two cents:
Setup one table with the jobs jobs:
job_id|job_name
Next, set up a table with drivers:
driver_id|driver_name
Now we need to maps:
First the "rules", drivers which are capable of jobs, job_capabilities:
driver_id|job_id
this will contain one row for each assignment job => driver, the combination (job_id, driver_id) should be unique - one driver is only one times capable of a particular job.
Second map contains the assignments itself, assigned_jobs:
driver_id|job_id
actually that has the same layout, but for a given time period (which is missing here) one driver actually can only work on one job, so driver_id and a date-time should be unique. Skipped for clearness now.
Now we can construct an SQL like
SELECT job_capabilities.driver_id, job.job_id from jobs, job_capabilities
where job.job_id = job_capabilities.job_id
AND job.job_id = 42;
We could just use that to insert into assigned_jobs with
INSERT INTO assigned_jobs .... (Select from above) ...
probably enhanced by a ON DUPLACET KEY UPDATE ... clause.
To now get the assigned jobs, we can alter that statement a bit:
SELECT assigned_jobs.driver_id, drivers.driver_name, job.job_id, job.job_name
from drivers, jobs, assigned_jobs
where job.job_id = assigned_jobs.job_id
AND drivers.driver_id = assigned_jobs.driver_id
AND job.job_id = 42;
This is not tested and probably not valid SQL, but a first approach I would use.
I am developing an evaluation system for different programs that needs a lot of flexibility. Each program will have different things to track, so I need to store what data points they want to track, and the corresponding data for the person being evaluated on the particular data point. I am guessing several tables are appropriate. Here is a general outline:
Table: accounts
- unique ID assigned to each account. We'll call this 'aid'
Table: users
- each user with unique ID.
Table: evaluation
- each program will enter in the metrics they want to track into this table (i.e attendance)
- column 'aid' will correspond to 'aid' in account table
Table: evaluation_data
- data (i.e attendance) entered into this database
- column 'aid' will correspond to 'aid' in account table
- column 'uid' will correspond to 'uid' in user table
The input form for evaluation_data will be generated from what's in the evaluation table.
This is the only logical way I can think of doing this. Some of these tables will be growing quite large over time. Is this the most optimal way of doing this?
I'm a little confused about how accounts, users and programs all relate to each other and whether or not account and program are the same thing and that you used the terms interchangeably. I'm going to use different terms which are just easier for me to understand.
Say you have a website that allows freelancers to keep track of different projects and they can create their own data to track. (Hope you see the similarity)
Tables...
freelancers
id title etc
projects
id freelancer_id title description etc
data_options
id freelancer_id title
You can even add other columns like data_type and give options like URL, email, text, date, etc which can be used for validation or to help format the input form.
example data:
1 5 Status
2 5 Budget
3 5 Customer
4 99 Job Type
5 99 Deadline
6 102 Price
7 102 Status
8 102 Due By
This display 3 different freelancers tracking data, freelancers with the id's 5, 99, and 102. Deadline and Due By are essentially the same but freelancers can call these whatever they want.
data_values
id project_id option_id option_value
a column freelancer_id as you would be able to to a join and get the freelancer_id from either the project_id or the option_id
example data:
1000 1 2 $250
1001 1 1 Completed
1002 1 3 Martha Hayes
This is only showing information freelancer with the id 5 has input because option_id's 1-3 belong to that user.
Hey. I have 160 columns that are filled with data when a user fills a report form out and submit it. A few of these sets of columns contain similar data, but there needs to be multiple instance of this data per record set as it may be different per instance in the report.
For example, an employee opens a case by a certain type at one point in the day, then at another point in the day they open another case of a different type. I want to create totals per user based on the values in these columns. There is one column set that I want to target right now, case type. I would like to be able to see all instances of the value "TSTO" in columns CT1, CT2, CT3... through CT20. Then have that sorted by the employee ID number, which is just one column in the table.
Any ideas? I am struggling with this one.
So far I have SELECT CT1, CT2, CT3, CT4, CT5, CT6, CT7, CT8, CT9, CT10, CT11, CT12, CT13, CT14, CT15, CT16, CT17, CT18, CT19, CT20 FROM REPORTS GROUP BY OFFICER
This will display the values of all the case type entries in a record set but I need to count them, I tried to use,
SELECT CT1, CT2, CT3, CT4, CT5, CT6, CT7, CT8, CT9, CT10, CT11, CT12, CT13, CT14, CT15, CT16, CT17, CT18, CT19, CT20 FROM REPORTS COUNT(TSTO) GROUP BY OFFICER
but it just spits an error. I am fairly new to mysql databasing and php, I feel I have a good grasp but query'ing the database and the syntax involved is a tad bit confused and/or overwhelming right now. Just gotta learn the language. I will keep looking and I have found some similar things on here but I don't understand what I am looking at (completely) and I would like to shy away from using code that "works" but I don't understand fully.
Thank you very much :)
Edit -
So this database is an activity report server for the days work for the employees. The person will often open cases during the day. These cases vary in type, and their different types are designated by a four letter convention. So your different case types could be TSTO, DOME, ASBA, etc etc. So the user will fill out their form throughout the day then submit it down to the database. That's all fine :) Now I am trying to build a page which will query the database by user request for statistics of a user's activities. So right now I am trying to generate statistics. Specifically, I want to be able to generate the statistic of, and in human terms, "HOW MANY OCCURENCES OF "USER INPUTTED CASE TYPE" ARE THERE FOR EMPLOYEEIDXXX"
So when a user submits a form they will type in this four letter case type up to 20 times in one form, there is 20 fields for this case type entry, thus there is 20 columns. So these 20 columns for case type will be in one record set, one record set is generated per report. Another column that is generated is the employeeid column, which basically identifies who generated the record set through their form.
So I would like to be able to query all 20 columns of case type, across all record sets, for a defined type of case (TSTO, DOME, ASBA, etc etc) and then group that to corresponding user(s).
So the output would look something like,
316 TSTO's for employeeid108
I hope this helps to clear it up a bit. Again I am fairly fresh to all of this so I am not the best with the vernacular and best practices etc etc...
Thanks so much :)
Edit 2 -
So to further elaborate on what I have going on, I have an HTML form that has 164 fields. Each of these fields ultimately puts a value into a column in a single record set in my DB, each submission. I couldn't post images or more than two URLs so I will try to explain it the best I can without screenshots.
So what happens is this information gets in the DB. Then there is the query'ing. I have a search page which uses an HTML form to select the type of information to be searched for. It then displays a synopsis of each report that matches the query. The user than enters the REPORT ID # for the report they want to view in full into another small form (an input field with a submit button) which brings them to a page with the full report displayed when they click submit.
So right now I am trying to do totals and realizing my DB will be needing some work and tweaking to make it easier to create querys for it for different information needed. I've gleaned some good information so far and will continue to try and provide concise information about my setup as best I can.
Thanks.
Edit 3 -
Maybe you can go to my photobucket and check them out, should let me do one link, there is five screenshots, you can kind of see better what I have happening there.
http://s1082.photobucket.com/albums/j376/hughessa
:)
The query you are looking for would be very long and complicated for your current db schema.
Every table like (some_id, column1, column2, column3, column4... ) where columns store the same type of data can be also represented by a table (some_id, column_number, column_value ) where instead of 1 row with values for 20 columns you have 20 rows.
So your table should rather look like:
officer ct_number ct_value
1 CT1 TSTO
1 CT2 DOME
1 CT3 TSTO
1 CT4 ASBA
(...)
2 CT1 DOME
2 CT2 TSTO
For a table like this if you wanted to find how many occurences of different ct_values are there for officer 1 you would use a simple query:
SELECT officer, ct_value, count(ct_value) AS ct_count
FROM reports WHERE officer=1 GROUP BY ct_value
giving results
officer ct_value ct_count
1 TSTO 2
1 DOME 1
1 ASBA 1
If you wanted to find out how many TSTO's are there for different officers you would use:
SELECT officer, ct_value, count( officer ) as ct_count FROM reports
WHERE ct_value='TSTO' GROUP BY officer
giving results
officer ct_value ct_count
1 TSTO 2
2 TSTO 1
Also any type of query for your old schema can be easily converted to new schema.
However if you need store additional information about every particular report I suggest having two tables:
Submissions
submission_id report_id ct_number ct_value
primary key
auto-increment
------------------------------------------------
1 1 CT1 TSTO
2 1 CT2 DOME
3 1 CT3 TSTO
4 1 CT4 ASBA
5 2 CT1 DOME
6 2 CT2 TSTO
with report_id pointing to a record in another table with as many columns as you need for additional data:
Reports
report_id officer date some_other_data
primary key
auto-increment
--------------------------------------------------------------------
1 1 2011-04-29 11:28:15 Everything went ok
2 2 2011-04-29 14:01:00 There were troubles
Example:
How many TSTO's are there for different officers:
SELECT r.officer, s.ct_value, count( officer ) as ct_count
FROM submissions s JOIN reports r ON s.report_id = r.report_id
WHERE s.ct_value='TSTO'
GROUP BY r.officer