ActiveRecord's query interface seems for me sometimes very complex and not intuitive. Is there a possibility to view in which SQL query results Rails construction I have written?
If you look in the console with the web server running, you will see what the ActiveRecord queries are compiled into. Additionally, you can open up the Rails console (rails console) and inspect them manually.
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What is the difference between a query builder and an ORM that developers use in their backend server-side code/logic for interacting with their database? It seems like the query builder can fulfill the goal of coding in the same language you are choosing to write the backend server-side code/logic to work with the database. However, I don't understand why an ORM comes in the picture then.
SQL query returns records (scalars) that do not automatically load more data if needed.
ORM can return you a Java object (say Person) with actual working methods that can load more data from database (without writing more queries explicitly).
For example if you call person.getAddress() it can return Address object that's just loads from database on the fly. Without writing new "select address" query.
Whatever is returned form SQL query (builder) does not work like that.
I have an ecommerce application that I believe is not properly caching all of our images and so I would like to capture all the queries that are occurring against our images table.
I need to be able to do this without installing anything or adding any code to the solution.
Can this be accomplished with SQL Profiler or another tool that does not require code modification?
The SQL Profiler is indeed the right tool for this.
You can attach it to your database, set some filters (for example, the text should contain the table name) and what events to log and off you go.
SQL Profiler will capture the queries as you have identified, you could also inspect the query cache, but it would not necessarily have all of the queries against that table still in cache, so should not be relied on.
We are working on a sync application using ColdFusion 9.0.1 ActionScript ORM Library for AIR applications. Since this is application should work smoothly offline as well, there is a list of clients that has to be loaded when a user logs in, hence we are fetching data from all the required tables when application loads (is that the right way?). Now when we get the data from the required tables then based on the user who logs in we have to filter the clients, to filter this the query required is a complex one with joins between 5-6 tables and where clause. What I found that using the Coldfusion.Air.Session class we can only load objects of tables with simple where clause. There is non ORM way to load the data but I don't think that is the right method. Is there any method using this ORM framework to load data using such complex queries.
Thanks,
Gaurav
Are you using any CF code to send data back to your application? Have you tried HQL?
In other words you can write standard cfquery and dbtype="hql"
This will let you do almost anything you can do with a standard cfquery.
I am not directly familiar with the ActionScript ORM Library for AIR.
In the application I'm developing, I am using NHibernate as ORM.
My app has to support SQL Server, and MS Access (I'm using the NHibernate JetDriver).
Now, the thing is that I have a certain query which I cannot achieve using HQL or the ICriteria API; so, I'm using an ISQLQuery for that one.
Now, what bothers me, is that it seems that NHibernate is parsing the native SQL query as well, and thereby changing the SQL code of that query.
It seems that the specific Driver implementation is called, and my query is parsed; and in the case of the JetDRiver, the query is being modified by NHibernate which results in a query that is unexecutable.
So, why is it that NHibernate changes my native SQL queries ?
NHibernate does some changes even in native queries in order to be able to map the entities correctly.
My suggestion... download the JetDriver source from https://nhcontrib.svn.sourceforge.net/svnroot/nhcontrib/trunk/src/NHibernate.JetDriver/ and debug to see what's being broken. It might be a bug there.
So I am new to Rails, so pardon the basic question.
I see rails spits this out (in the console) for every request I make to my controller. Why? I'm not even doing any DB operation, I just started writing a HelloWorld rails app. I did pick mysql as the db when creating this rails project (rails -d mysql helloworld)
SQL (0.1ms) SET NAMES 'utf8'
SQL (0.1ms) SET SQL_AUTO_IS_NULL=0
So I noticed, that rails attempts to establish a DB connection for every request, irrespective whether you do a DB/ActiveRecord operation. It does this right after it does action_controller/dispatch. This seems like a waste of DB resource to me, why establish a connection to DB when I may not even do a ActiveRecord operation??
You're seeing this on every request because you're in development mode. In production mode (or with class caching turned on), this only happens once, when the connection is added to the connection pool.