I have objects that users can buy to use.
Backpacks. Backpacks have different types so I was thinking I would use STI as described in the doctrine docs:
http://docs.doctrine-project.org/en/2.0.x/reference/inheritance-mapping.html#single-table-inheritance
This is fine, and works. Someone can buy a BasicBackPack, or a LargeBackPack and the correct class is created when the entity is collected from the repository.
This all works fine.
My problem now is, is that I want people to be able to upgrade a BasicBackPack to a LargeBackPack but I find I can't changethe descriminator column value. When ever I try doctrine complains that there is no "descriminatorColumn" in class x, but there is as I can see it in the database.
Is it not possible to change the descrimnator column value once an entity is made?
Related
Can Django support Oracle nested tables or varrays or collections in some manner? Asking just for completeness as our project is reworking the data model, attempting to move away from EAV organization, but I don't like creating a bucket load of dependent supporting tables for each main entity.
e.g.
(not the proper Oracle syntax, but gets the idea across)
Events
eventid
report_id
result_tuple (result_type_id, result_value)
anomaly_tuple(anomaly_type_id, anomaly_value)
contributing_factors_tuple(cf_type_id, cf_value)
etc,
where the can be multiple rows of the tuples for one eventid
each of these tuples can, of course exist as separate tables, but this seems to be more concise. If it 's something Django can't do, or I can't modify the model classes to do easily, then perhaps just having django create the extra tables is the way to go.
--edit--
I note that django-hstore is doing something very similar to what I want to do, but using postgresql's hstore capability. Maybe I can branch off of that for an Oracle nested table implementation. I dunno...I'm pretty new to python and django, so my reach may exceed my grasp in this case.
Querying a nested table gives you a cursor to traverse the tuples, one member of which is yet another cursor, so you can get the rows from the nested table.
I am trying to retrieve a single row from a table. This row contains filed that hold foreign keys into another table, which in turns is related to yet another table. I am trying to get just one row returned, yet, the problem is, it returns not only the row but ALL the objects that are jointly related to that table as well. As I have to deal with a fairly large amount of data, the returned object is very cumbersome as it contains all the related data as well. In some cases my script simply times out because there is just far too much data to grab.
My question is; is there a way to retrieve just a single record without the associated fluff with it? I am basically accessing the table via the entityManager from the repository, then trying to get my record by using the ->find($id) method.
I am sure this is something stupidly simple but I can't seem to figure this out. Thanks in advance for any help, it is much appreciated.
Doctrine 2 use "lazy loading", it means that the associated objects are not really retrieved from the database while you don't try to access them.
So the find($id) is just fine.
I need to make a query like this:
SELECT PNPDeviceID FROM Win32_NetworkAdapter WHERE AdapterTypeId = 0
Trouble is, the AdapterTypeId column isn't always present. In this case, I just want everything, like so:
SELECT PNPDeviceID FROM Win32_NetworkAdapter
My WQL/SQL knowledge is extremely limited. Can anybody tell me how to do this in a single query?
EDIT:
A bit more background seems to be required: I am querying Windows for device information using WMI, which uses an SQL-like syntax. So, in my example, I am querying for network adapters that have an AdapterTypeId of 0.
That column is not always present however, meaning that if I enumerate through the returned values then "AdapterTypeId" is not listed.
EDIT 2:
Changed SQL to WQL; apparantly this is more correct.
I am assuming you mean the underlying schema is unreliable.
This is a highly unconventional situation. I suggest that you resolve the issue that is causing the column to not always be present, because to have the schema changing dynamically underneath your application is potentially (almost certainly) disastrous.
Update:
OK, so WQL lets you query objects with a SQL-like syntax but, unlike SQL, the schema can change underneath your feet. This is a classic example of a leaky abstraction, and I now hate WQL without ever having used it :).
Since the available properties are in flux, I am guessing that WQL provides a way to enumerate the properties for a given adapter. Do this, and choose which query to run depending upon the results.
After some Googling, there is an example here, which shows how to enumerate through the available properties. You can use this to determine if AdapterTypeId exists or not.
SELECT PNPDeviceID FROM Win32_NetworkAdapter WHERE AdapterTypeId = {yourDesire} OR AdapterTypeId IS NULL
I assume that you mean that this field is missing from the table.
Do you know before submitting the query if this field exists?
If yes then just create SQL dynamically, otherwise It think you will get syntax error in case of missing field
This is not an SQL question. SQL does not contemplate records with varying schemas in a single table source. Instead (as you mention) this is a different system using an "SQL-like" syntax. You'll have better luck if you recast the question using the actual product that you're trying to query, and information how that product deals with variable record structures is probably discussed in the documentation.
I have a simple database and want to update an int value. I initially do a query and get back a ResultSet (sql::ResultSet). For each of the entries in the result set I want to modify a value that is in one particular column of a table, then write it back out to the database/update that entry in that row.
It is not clear to me based on the documentation how to do that. I keep seeing "Insert" statements along with updates - but I don't think that is what I want - I want to keep most of the row of data intact - just update one column.
Can someone point me to some sample code or other clear reference/resource?
EDIT:
Alternatively, is there a way to tell the database to update a particular field (row/col) to increment an int value by some value?
EDIT:
So what is the typical way that people use MySQL from C++? Use the C api or the mysql++? I guess I chose the wrong API...
From a quick scan of the docs it appears Connector/C++ is a partial implementation of the Java JDBC API for C++. I didn't find any reference to updateable result sets so this might not be possible. In Java JDBC the ResultSet interface includes support for updating the current row if the statement was created with ResultSet.CONCUR_UPDATABLE concurrency.
You should investigate whether Connector/C++ supports updateable resultsets.
EDIT: To update a row you will need to use a PreparedStatement containing an SQL UPDATE, and then the statement's executeUpdate() method. With this approach you must identify the record to be update with a WHERE clause. For example
update users set userName='John Doe' where userID=?
Then you would create a PreparedStatement, set the parameter value, and then executeUpdate().
I'm trying to do a proof of concept using SubSonic 3 but Sstraight away i'm hitting numerous errors with the generation. I started making alterations to the generator settings but that seems a little odd when I'm just trying to do a simple one to one mapping of my DB.
Firstly I found an SP that had #delagate as an SP parameter name, this was easily fixed, but should probably be in the standard templates as a user shouldn't have to make template changes for this simple an issue.
Next I found that the system choked on two tables and tried to create signatures the same
the tables where
Field
Fields
now i know SubSonix 2 had a fixPluralClassName property but buggered if I can find one in the template for SubSonic 3
Any help on that one will get me started
Generally 'X' and 'Datum' type appendages/substitutions happen when you have used a 'reserved' word in a column or table name. In this case 'Reserved' being a word that Subsonic doesn't like to use for data objects.
A couple of rules I follow are;
Ensure both table names and column
names are not 'reserved' words (ie
'Data' or 'Int' or 'Table')
Ensure that each table has a primary key
Don't use date and time column types
as they are not supported yet
(DateTime is, just not Date and Time types)
Don't have a column with the same
name as the table
The Subsonic FAQ might be helpful.