With Django it is possible to find models using the filter method with keyword-arguments like so:
MyModel.objects.filter(serialNo_gt=10)
giving all models with a serial number greater than 10.
Is it possibly to use a similar query language with sql-alchemy? I know that one can write something like MyModel.seriealNO < 10, but with that the code that uses this construct need to import MyModel and I want to create the keywords/query parameters externally without importing MyModel (for a facade-pattern).
the concept of "<attributename>_<operatorname>=<value>" is not built in to SQLAlchemy's Query, however the effect is very easy to reproduce. Here's a quick example done by the author of Flask: https://github.com/mitsuhiko/sqlalchemy-django-query/blob/master/sqlalchemy_django_query.py
Related
I'm writing an application using OWL-API and Hermit Reasoner. I would like to query data using SPARQL-DL by submitting query like:
PREFIX wine: <http://www.w3.org/TR/2003/PR-owl-guide-20031209/wine#>
SELECT ?i
WHERE { Type(?i, wine:PinotBlanc) }
OR WHERE { Type(?i, wine:DryRedWine) }
Can I Do this directy with owl-api or should I use an external library (http://www.derivo.de/en/resources/sparql-dl-api/ ) ? ( I need something like
queryEngine.query(my_query); )
As in July 2013, the OWL-API does not support natively SPARQL-DL. You need to plug a third party library in order to make it work.
I am aware of two implementations (there's maybe more): One by Derivo (your link) and another one by Pellet.
I used OWL-API with Hermit and Pellet; both worked fine. The advantage of Pellet over Hermit is that it supports built-ins.
i.e. In Pellet, for some class Teenager, you can get seventeen year old persons using the following query:
Person and (hasAge value "17.0"^^double)
If you (or somebody) are still interested in, I can provide the Java class for it.
A pure OWL-API-impl cannot provide non-workaround way to support SPARQL since it is not graph based solution.
Now, starting v5, there is ONT-API which is jena-based OWL-API impl.
I have this use case where I get the symbolized deep associations from a certain model, and I have to perform certain queries that involve using outer joins. How can one do it WITHOUT resorting to write the full SQL by hand?
Answers I don't want:
- using includes (doesn't solve deep associations very well ( .includes(:cars => [:windows, :engine => [:ignition]..... works unexpectedly ) and I don't want its side-effects)
- writing the SQL myself (sorry, it's 2013, cross-db support, etc etc..., and the objects I fetch are read_only, more side-effects)
I'd like to have an Arel solution. I know that using the arel_table's from the models I can construct SQL expressions, there's also a DSL for the joins, but somehow i cannot use it in the joins method from the model:
car = Car.arel_table
engine = Engine.arel_table
eng_exp = car.join(engine).on(car[:engine_id].eq(engine[:id]))
eng_exp.to_sql #=> GOOD! very nice!
Car.joins(eng_exp) #=> Breaks!!
Why this doesn't work is beyond me. I don't know exactly what is missing. But it's the closest thing to a solution I have now. If somebody could help me completing my example or provide me with a nice work-around or tell me when will Rails include such an obviously necessary feature will have my everlasting gratitude.
This is an old question, but for the benefit of anyone finding it through search engines:
If you want something you can pass into .joins, you can either use .create_join and .create_on:
join_on = car.create_on(car[:engine_id].eq(engine[:id]))
eng_join = car.create_join(engine, join_on, Arel::Nodes::OuterJoin)
Car.joins(eng_join)
OR
use the .join_sources from your constructed join object:
eng_exp = car.join(engine, Arel::Nodes::OuterJoin).on(car[:engine_id].eq(engine[:id]))
Car.joins(eng_exp.join_sources)
I found a blog post that purports to address this problem: http://blog.donwilson.net/2011/11/constructing-a-less-than-simple-query-with-rails-and-arel/
Based on this (and my own testing), the following should work for your situation:
car = Car.arel_table
engine = Engine.arel_table
sql = car.project(car[Arel.star])
.join(engine, Arel::Nodes::OuterJoin).on(car[:engine_id].eq(engine[:id]))
Car.find_by_sql(sql)
If you don't mind adding a dependency and skipping AREL altogether, you could use Ernie Miller's excellent Squeel gem. It would be something like
Car.joins{engine.outer}.where(...)
This would require that the Car model be associated with Engine like so:
belongs_to :engine
I'm currently trying to create an Endeca query using the Java API for a URLENEQuery. The current query is:
collection()/record[CONTACT_ID = "xxxxx" and SALES_OFFICE = "yyyy"]
I need it to be:
collection()/record[(CONTACT_ID = "xxxxx" or CONTACT_ID = "zzzzz") and
SALES_OFFICE = "yyyy"]
Currently this is being done with an ERecSearchList with CONTACT_ID and the string I'm trying to match in an ERecSearch object, but I'm having difficulty figuring out how to get the UrlENEQuery to generate the or in the correct fashion as I have above. Does anyone know how I can do this?
One of us is confused on multiple levels:
Let me try to explain why I am confused:
If Contact_ID and Sales_Office are different dimensions, where Contact_ID is a multi-or dimension, then you don't need to use EQL (the xpath like language) to do anything. Just select the appropriate dimension values and your navigation state will reflect the query you are trying to build with XPATH. IE CONTACT_IDs "ORed together" with SALES_OFFICE "ANDed".
If you do have to use EQL, then the only way to modify it (provided that you have to modify it from the returned results) is via string manipulation.
ERecSearchList gives you ability to use "Search Within" functionality which functions completely different from the EQL filtering, though you can achieve similar results by using tricks like searching only specified field (which would be separate from the generic search interface") I am still not sure what's the connection between ERecSearchList and the EQL expression above?
Having expressed my confusion, I think what you need to do is to use String manipulation to dynamically build the EQL expression and add it to the Query.
A code example of what you are doing would be extremely helpful as well.
If I were retrieving the data I wanted from a plain sql query, the following would suffice:
select * from stvterm where stvterm_code > TT_STUDENT.STU_GENERAL.F_Get_Current_term()
I have a grails domain set up correctly for this table, and I can run the following code successfully:
def a = SaturnStvterm.findAll("from SaturnStvterm as s where id > 201797") as JSON
a.render(response)
return false
In other words, I can hardcode in the results from the Oracle function and have the HQL run correctly, but it chokes any way that I can figure to try it with the function. I have read through some of the documentation on Hibernate about using procs and functions, but I'm having trouble making much sense of it. Can anyone give me a hint as to the proper way to handle this?
Also, since I think it is probably relevant, there aren't any synonyms in place that would allow the function to be called without qualifying it as schema.package.function(). I'm sure that'll make things more difficult. This is all for Grails 1.3.7, though I could use a later version if needed.
To call a function in HQL, the SQL dialect must be aware of it. You can add your function at runtime in BootStrap.groovy like this:
import org.hibernate.dialect.function.SQLFunctionTemplate
import org.hibernate.Hibernate
def dialect = applicationContext.sessionFactory.dialect
def getCurrentTerm = new SQLFunctionTemplate(Hibernate.INTEGER, "TT_STUDENT.STU_GENERAL.F_Get_Current_term()")
dialect.registerFunction('F_Get_Current_term', getCurrentTerm)
Once registered, you should be able to call the function in your queries:
def a = SaturnStvterm.findAll("from SaturnStvterm as s where id > TT_STUDENT.STU_GENERAL.F_Get_Current_term()")
I previously asked a question regarding pulling specific items out of a database if they contained a specific word in their string, someone kindly offered the following which did just the job:
def SomeModel < ActiveRecord::Base
scope :contains_city,
lambda { |city| where("some_models.address LIKE ?","%"+city+"%" ) }
end
However, I have some instances where I would like to do the opposite, i.e. pull out all the items which do not have the specified word in their string. Is there a way to do a NOT LIKE function? I have prevously seen people use '!=' for a NOT EQUALS, but have had no success along these lines for the LIKE function. Is there an equivalent or is it best to iterate through the database putting items in 2 separate databases based on whether they satisfy the LIKE condition?
You could try NOT LIKE in your query; MySQL supports this.
http://dev.mysql.com/doc/refman/5.0/en/string-comparison-functions.html