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How can I define a composite primary key in SQL?
...rID)
);
The pair (QuestionID,MemberID) must then be unique for the table and neither value can be NULL. If you do a query like this:
SELECT * FROM voting WHERE QuestionID = 7
it will use the primary key's index. If however you do this:
SELECT * FROM voting WHERE MemberID = 7
it won't because...
What is the relative performance difference of if/else versus switch statement in Java?
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That's micro optimization and premature optimization, which are evil. Rather worry about readabililty and maintainability of the code in question. If there are more than two if/else blocks glued together or its size is unpredictable, then you may high...
What's the $unwind operator in MongoDB?
...om your mind. The way that it stores your data is in the form of documents and collections, which allows for a dynamic means of adding and obtaining the data from your storage locations.
That being said, in order to understand the concept behind the $unwind parameter, you first must understand what...
What is the $? (dollar question mark) variable in shell scripting? [duplicate]
I'm trying to learn shell scripting, and I need to understand someone else's code. What is the $? variable hold? I can't Google search the answer because they block punctuation characters.
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What is the Invariant Culture?
...xample to demonstrate the usage of the Invariant Culture ? I don't understand what the documentation describes.
5 Answers
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Objective-C declared @property attributes (nonatomic, copy, strong, weak)
...ail when I must use each attribute: nonatomic , copy , strong , weak , and so on, for a declared property, and explain what each does? Some sort of example would be great also. I am using ARC.
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How many concurrent requests does a single Flask process receive?
I'm building an app with Flask, but I don't know much about WSGI and it's HTTP base, Werkzeug. When I start serving a Flask application with gunicorn and 4 worker processes, does this mean that I can handle 4 concurrent requests?
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What is pluginManagement in Maven's pom.xml?
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The difference between <pluginManagement/> and <plugins/> is that a <plugin/> under:
<pluginManagement/> defines the settings for plugins that will be inherited by modules in your build. This is great for cases where you have a parent pom file.
<...
moment.js - UTC gives wrong date
...ded, the time defaults to midnight.
In your code, you create a local date and then convert it to the UTC timezone (in fact, it makes the moment instance switch to UTC mode), so when it is formatted, it is shifted (depending on your local time) forward or backwards.
If the local timezone is UTC+N (...
How to exclude specific folders or files from validation in Eclipse?
...of malformed XML files used in unit tests to check if our application can handle them.
6 Answers
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