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Difference between a theta join, equijoin and natural join
I'm having trouble understanding relational algebra when it comes to theta joins, equijoins and natural joins. Could someone please help me better understand it? If I use the = sign on a theta join is it exactly the same as just using a natural join?
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Uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)
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This is an incompatibility between Rails 2.3.8 and recent versions of RubyGems. Upgrade to the latest 2.3 version (2.3.11 as of today).
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What is a lambda (function)?
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Lambda comes from the Lambda Calculus and refers to anonymous functions in programming.
Why is this cool? It allows you to write quick throw away functions without naming them. It also provides a nice way to write closures. With that power you can do things like...
How to reposition Chrome Developer Tools
...p an option to change the docking
To change the split between the HTML and CSS panels, go in DevTools to Settings (F1) > General > Appearance > Panel Layout.
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newline in [duplicate]
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This should now work with Internet Explorer, Firefox v12+ and Chrome 28+
<img src="'../images/foo.gif'"
alt="line 1&#013;line 2" title="line 1&#013;line 2">
Try a JavaScript tooltip library for a better result, something like OverLib.
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What does the caret (^) character mean?
...that git commits can have more than one parent. HEAD^ is short for HEAD^1, and you can also address HEAD^2 and so on as appropriate.
You can get to parents of any commit, not just HEAD. You can also move back through generations: for example, master~2 means the grandparent of the tip of the master ...
Getting a structural type with an anonymous class's methods from a macro
...a macro that defines an anonymous class with some type members or methods, and then creates an instance of that class that's statically typed as a structural type with those methods, etc. This is possible with the macro system in 2.10.0, and the type member part is extremely easy:
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C/C++中的段错误（Segmentation fault） - C/C++ - 清泛网 - 专注C/C++及内核技术
...ress or Bus errors.
Segmentation is one approach to memory management and protection in the operating system. It has been superseded by paging for most purposes, but much of the terminology of segmentation is still used, "segmentation fault" being an example. Some operating systems still have s...
JPA : How to convert a native query result set to POJO class collection
...our result with the entity with tha java entity class with "@EntityResult" and "@FieldResult" annotations. Thats fine. But here i need more clarity. Is is required that the class which we are mapping with the result must be a JPA entity class ? OR can we use a simple POJO class which is not an enti...
How do I access call log for android?
... of Jellybean (4.1) you need the following permission:
<uses-permission android:name="android.permission.READ_CALL_LOG" />
Code:
Uri allCalls = Uri.parse("content://call_log/calls");
Cursor c = managedQuery(allCalls, null, null, null, null);
String num= c.getString(c.getColumnIndex(CallLo...