I currently have about 4 different database tables which output to html tables. Each of these tables uses a count query to calculate data from a 5th table.
That's no problem, but what about when I want to sort and order the data, and paginate etc (like with zend). If it were a one page table, I could probably sort an array.
My thought was, to use a ticker. But that would require a new column in all 4 tables and seems like overkill or like there could be a better way.
Sadly, I can't find much info on it (likely because I don't know what to search for).
Advice?
..and please take it easy, I'm new and learning.
Assuming youre using Zend_Db_Table_Row and that you dont need to persist any modifications you might make to these rowsets then you can just append the virtual columns to the row object and have them be accessible via array notation. So if youre doing it all in one query now just use that same query, and the column should be there.
OTOH, if youre using a Data Mapper pattern then simply adjust your hydration to look for this "virtual column" and hydrate it if it exists in the result data. Then in your getter for this property have it see if the property is null or some other negative specification, and if it is, to execute a calculation query on that single object or return the already calculated result.
Related
I have ran into a predicament on this system I have been working on. In the table "class" there are multiple rows of classes. The column I am focusing on is "dates". On the admin dashboard, I need to be able to list the classes by the closest date to the farthest away. I tried using this but it does not work the way I want it to.
mysqli_query("SELECT * FROM class ORDER BY dates ASC")
My problem is that the column "dates" is actually a serialized array of the start and end dates. Because of this I can't use strtotime() to make the above code work 100% correctly.
My overall question is, is there any way I can sort a query by a serialized date string?
I know opinions of different ways to do it will arise, but that's not what I'm shooting for. If it is possible or you have any idea, please post an answer.
mysql order by serialized data?
No, it is not possible. The only possible case when serialized data is acceptable is when you don't need to search or order by through that data. In all other cases - store your data as a separated fields.
Let's say I have a DbTable_Product table class that represents a table product. When I query that table i.e.
$myProducts = $productTable->fetchAll();
I get a resultset of DbTableRow_Product objects. This is fine and it's the way I've done it forever.
I've just now come up against a problem for a second time in two projects, in which I want to be more specific with the object types returned in the resultset.
For instance, let's say almost all of the products don't have any special behaviour, so using the generic DbTableRow_Product class is suitable for them. But there is one difficult product that does need additional behavior.
Say there's a class I've created called DbTableRow_Product_Phone that inherits from DbTableRow_Product. I want the table object to return DbTableRow_Product objects when the resulting row is not a phone, and DbTableRow_Product_Phone when it is, all in the same resultset.
I've done this in a previous project by overriding the fetchRow, fetchAll, getRowClass and createRow methods in the table object to create the correct type of object. This works but it seems dirty.
Is there an easier way of creating different object types in a resultset, depending on the type of row? Does this approach even make sense?
So, there's a field in the db in which I store serialized arrays.
$array = array('count1' => 10, 'count2' => 20, 'count3' => 4);
serialized:
a:3:{s:6:"count1";i:10;s:6:"count2";i:20;s:6:"count3";i:4;}
Would it be possible to pull count1+count2+count3 using a mysql query? I guess I'm looking for something like php's explode. Pretty sure this can't be done, but I thought I'd ask.
I need to pull the highest count1+count2+count3 rows and return the total count. Looping through each row and unserializing wouldn't work since there are TONS of rows.
If you need to access parts of your serialized data via SQL, you need to store them in separate columns.
While it might be possible to use techniques such as regular expressions to access those three values in this string, it would be extremely slow when used in a WHERE criterion as indexes would be useless - not to mention that it would be a huge mess, way worse than using goto in a programming language.
So the solution is to create a new columns and then iterate over all rows, unserialize them, and store the sum into the new column. That might take a while but you'll only need to it once.
Depending on your application it might be better to create three columns and store each value separately.
Suppose we have two related tables, for example one representing a person:
PERSON
name
age
...
current_status_id
and one representing a status update at a specific time for this person:
STATUS_HISTORY
recorded_on
status_id
blood_pressure
length
...
I have built an application in PHP using Zend Framework, and tried to retain 'object orientedness' by using a class for representing a person and a class for representing the status of a person. I also tried to use ORM principles where possible, such as using the data mapper for separating the domain model from the data layer.
What would be a nice (and object oriented) way of returning a list of persons from a data mapper, where in the list I sometimes want to know the last measured blood_pressure of the person, and sometimes not (depending on the requirements of the report/view in which the list is used). The same holds for different fields, e.g. values computed at the data layer (sum's, count's, etc.).
My first thought was using a rowset (e.g. Zend_Db_Rowset) but this introduces high coupling between my view and data layer. Another way might be to return a list of persons, and then querying for each person the latest status using a data mapper for requesting the status of a specific person. However, this will result in (at least) one additional query for each person record, and does not allow me to use JOINS at the data layer.
Any suggestions?
We have this same issue because of our ORM where I work. If you are worried enough about the performance hit of having to first get a list of your persons, then query for their statuses individually, you really have no other choice but to couple your data a little bit.
In my opinion, this is okay. You can either create a class that will hold the single "person" data and an array containing "status_history" records or suffer the performance hit of making another query per "person". You COULD reduce your query overhead by doing data caching locally (your controller would have to decide that if a request for a set of data is made before a certain time threshold, it just returns its own data instead of querying the db server)
Having a pure OO view is nice, but sometimes impractical.
Try to use "stdclass" class which is PHP's inbuild class, You can get the object of stdclass which will be created automatically by PHP and its member variable will be column name. So u can get object and get the values by column name. For example.
Query is
SELECT a.dept_id,a.dept_name,a.e_id,b.emp_name,b.emp_id from DEPT a,EMP b where b.emp_id=a.e_id;
Result will be array of stdclass objects. Each row represents one stdclass object.
Object
STDCLASS
{
dept_id;
dept_name;
e_id;
emp_id;
emp_name;
}
You can access like
foreach($resultset as $row)
{
$d_id = $row->dept_id;
$d_nam= $row->dept_name;
$e_id = $row->e_id;
$em_id= $row->emp_id;
$e_nam= $row->emp_name;
}
But
Blockquote
I am not sure about performance.
I have a MySQL database containing these tables:
sessions
--------
sessionid (INT)
[courseid (INT)]
[locationid (INT)]
[comment (TEXT)]
dates
-----
dateid (INT)
sessionid (INT)
date (DATE)
courses
-------
...
locations
---------
...
Each session has a unique sessionid, and each date has a unique dateid. But dates don't necessarily have a unique sessionid, as a session can span over a variable number of dates (not necessarily consecutive).
Selecting each full row is simply a matter of joining the tables on the sessionid. However, I'm looking for a way to return a rowset for a particular courseid, where each row in that rowset represents a location, and contains another rowset, each containing single session, which in turn contains another rowset, which contains all of the dates for that session:
course
location
sesssion
date
date
session
date
date
date
location
...
This is because I'm using querying this database from PHP using Zend Framework, which has a great interface for manipulating rows and rowsets in an object-oriented manner.
Ultimately, I'm trying to output a 'schedule' to the view, organized first by course, then location, then date. Ideally, I'd be able iterate over each row as a location, and then for each location, iterate over each session, and then for each session, iterate over each date.
I'm thinking of doing this by querying for all the locations, sessions, and dates separately. Then, I'd convert each rowset into an array, and add each sessions array as a member of a locations array, and add each dates array as a member of a sessions array.
This, however, feels very kludgy, and doesn't provide me with the ability to handle the rows in an object-oriented manner.
I was wondering if there was either:
a) a better table schema for representing this data;
b) an sql query which i'm not aware of;
c) a method in Zend_Db that allows me to assign a rowset to a rowset
Please let me know if I haven't been clear anywhere, and thanks in advance.
(Crossing my fingers that this doesn't end up on the daily wtf...)
I've run into lots of issues with using Zend Frameworks database abstraction classes when I have to deal with data from multiple tables. The number of queries that run and the overhead of all of the objects generated has brought my hosting server to it's knees. I've since reverted back to writing queries to gather all of my data and then walking the data to build my display. It's not a pretty or OO as using the abstraction layers but it's also not making my PHP scripts page to disk just to display a table full of data.
As Steve mentions benchmark whatever solution you end up with, I'd also profile your memory usage.
You could handle this scenario using the relationship features of Zend_ Db_ Table. You'd need to create table wrapper classes for sessions, dates, courses, etc. if you're using Zend_ Db_ Aadpter for your queries currently.
http://framework.zend.com/manual/en/zend.db.table.relationships.html
It's not too different from the approach you described of querying for each dataset separately, but it gives you a straight forward OO interface for retrieving the appropriate related data for a given record.
You'll want to do some benchmarking if you go this route, as it could potentially execute a lot of queries.