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What's wrong with nullable columns in composite primary keys?
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Primary keys are for uniquely identifying rows. This is done by comparing all parts of a key to the input.
Per definition, NULL cannot be part of a successful comparison. Even a comparison to itself (NULL = NULL) will fail. This means a key containing NULL would not work.
Additonally, NULL is al...
Calling constructors in c++ without new
...d the most common way of creating new dynamic objects instead of using auto_ptr, unique_ptr, or related.
– Fred Nurk
Jan 18 '11 at 13:18
3
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Python concatenate text files
...new file. I could open each file by f = open(...) , read line by line by calling f.readline() , and write each line into that new file. It doesn't seem very "elegant" to me, especially the part where I have to read//write line by line.
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Session variables in ASP.NET MVC
I am writing a web application that will allow a user to browse to multiple web pages within the website making certain requests. All information that the user inputs will be stored in an object that I created. The problem is that I need this object to be accessed from any part of the website and I ...
how do you filter pandas dataframes by multiple columns
...r function using query in pandas. Here you have filtering of df results by all the kwargs parameters. Dont' forgot to add some validators(kwargs filtering) to get filter function for your own df.
def filter(df, **kwargs):
query_list = []
for key in kwargs.keys():
query_list.append(f...
How to delete an object by id with entity framework
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The same as @Nix with a small change to be strongly typed:
If you don't want to query for it just create an entity, and then delete it.
Customer customer = new Customer () { Id = id };
context.Customers.Attach(custome...
Pretty print in MongoDB shell as default
...y, everything is output to a single line and it's difficult to read, especially with nested arrays and documents.
8 Answers...
Can't find Request.GetOwinContext
...uget package (The nuget package name is Microsoft.AspNet.WebApi.Owin)
Install-Package Microsoft.AspNet.WebApi.Owin
See msdn here: http://msdn.microsoft.com/en-us/library/system.net.http.owinhttprequestmessageextensions.getowincontext(v=vs.118).aspx
Nuget package here: https://www.nuget.org/packa...
How do I print a double value with full precision using cout?
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Is the really the right answer? When I manually use a high number, I can print out as many as 51 digits of approximated e, but with cout.precision(numeric_limits<double>::digits10 + 2); I only get 16....
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Call a “local” function within module.exports from another function in module.exports?
How do you call a function from within another function in a module.exports declaration?
8 Answers
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