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Hello,
I have a class that derives from ActiveRecord::Base. This class has a subclass that is differentiated in the database by a type id column. How do I make sure that all the inherited active record functions in the derived classes append the type_...
Started by Mattew on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
That's why what Radar said about your column being.
Are doing is called Single Table Inheritance (STI).
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Let's say I need to query the associates of a corporation. I have a table, "transactions", which contains data on every transaction made.
CREATE TABLE `transactions` ( `transactionID` int(11) unsigned NOT NULL, `orderID` int(11) unsigned NOT NULL, `customerID...
Started by FRKT on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
At some point in there, as your query joins the transaction table to the transaction table.
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Sometimes we can write a query with both derived table and temporary table. my question is that which one is better? why?
Started by masoud ramezani on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
Derived....
Derived table is better as temporary tables become more complex when its is used more and more
A derived table is the result of using another SELECT statement in the FROM clause of a SELECT statement.
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I have an abstract base class for audit properties. For brevity say it has one property
Public MustInherit Class AbstractAuditableEntity ... Public Property CreatedTime() As DateTimeOffset ... End Class
And then my auditable domain objects inherit from...
Started by cpedros on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
It works great if you database table map more or less 1:1 to your domain.
Of the limitations of Linq-to-SQL.
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I'm not sure of the terminology here, so let me give an example. I have this query:
SELECT * FROM Events Id Name StartPeriodId EndPeriodId 1 MyEvent 34 32
In here, the PeriodIds specify how long the event lasts for, think of it as weeks of the year specified...
Started by colinramsay on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Using these two date it joins with the periods table on values inside.
Specified on the event.
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What's the difference between a derived object and a base object in c++,
especially, when there is a virtual function in the class.
Does the derived object maintain additional tables to hold the pointers
to functions?
Started by MainID on
, 12 posts
by 12 people.
Answer Snippets (Read the full thread at stackoverflow):
derived - is the object the....
The respective objects' representation in memory?
Both the base class and the derived class will have a tableDerived is Base, but Base is not a Derived
base- is the object you are deriving from.
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On Thu, 27 Dec 2007 12:02:12 +0800, "wang shuming" <wangshuming01@gmail.com> wrote:
Hi,
select * , ( select f2
from (select f1,f2 from t2 where t2.id=t1.id limit 1 union
all ... order by f1 ) t2
limit ...
Started by wang shuming on
, 2 posts
by 2 people.
Answer Snippets (Read the full thread at omgili):
On Thu, 27 Dec 2007 08:21:51 -0500, "Baron Schwartz" <baron@xaprb.com> wrote:
Hi,
On Dec 26, 2007 11:02 PM, wang shuming <wangshuming01@gmail.com> wrote:
> Hi,
> select * , ( select f2
> from (select f1,f2... .
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Update: the shared_ptr in this example is like the one in Boost, but it doesn't support shared_polymorphic_downcast (or dynamic_pointer_cast or static_pointer_cast for that matter)!
I'm trying to initialize a shared pointer to a derived class without ...
Started by Lajos Nagy on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
() { } }; // dynamic casts require polymorphic types struct Derived : public Base { }; boost::shared_ptr<Base> base(new Base()); boost::shared_ptr<Derived> derived; derived = boost::static_pointer_cast<Derived>(base....
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Hi,
Check the screen shot of the universe in question here.
"GROUPING_COUNTY" is a derived table that is grouping County Names in a single row by Location ID and State Code. Their is a left outer join between Project table and the derived table.
Report...
Started by Adnan on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at forumtopics):
Problem with derived table is that it will add entire derived table SQL in the query, causing major performance issues at run time, try to create table.
To this, because it creates the cartisian results.
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Can someone please put me out of my misery with this? I'm trying to figure out why a derived operator== never gets called in a loop. To simplify the example, here's my Base and Derived class:
class Base { // ... snipped bool operator==( const Base& other...
Started by Robin Welch on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
For derived classes to....
It sounds like you want to look could have an overloaded operator== in your derived class that would be able to handle Derived objects.
From base to derived, you are actually creating a new function.
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