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Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails
I'm having a bit of a strange problem. I'm trying to add a foreign key to one table that references another, but it is failing for some reason. With my limited knowledge of MySQL, the only thing that could possibly be suspect is that there is a foreign key on a different table referencing the one I ...
What's the best way to set a single pixel in an HTML5 canvas?
The HTML5 Canvas has no method for explicitly setting a single pixel.
14 Answers
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Can you explain the HttpURLConnection connection process?
I am using HTTPURLConnection to connect to a web service. I know how to use HTTPURLConnection but I want to understand how it works. Basically, I want to know the following:
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Determine if the device is a smartphone or tablet? [duplicate]
I would like to get info about a device to see if it's a smartphone or tablet. How can I do it?
9 Answers
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What are bitwise shift (bit-shift) operators and how do they work?
I've been attempting to learn C in my spare time, and other languages (C#, Java, etc.) have the same concept (and often the same operators) ...
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How do I get the type of a variable?
In C++, how does one find the type of a variable?
10 Answers
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Is there a CSS parent selector?
How do I select the <li> element that is a direct parent of the anchor element?
33 Answers
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JavaScript pattern for multiple constructors
I need different constructors for my instances. What is a common pattern for that?
9 Answers
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Reorder / reset auto increment primary key
I have a MySQL table with an auto increment primary key. I deleted some rows in the middle of the table. Now I have, for example, something like this in the ID column: 12, 13, 14, 19, 20. I deleted the 15, 16, 17 and 18 rows.
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What goes into the “Controller” in “MVC”?
I think I understand the basic concepts of MVC - the Model contains the data and behaviour of the application, the View is responsible for displaying it to the user and the Controller deals with user input. What I'm uncertain about is exactly what goes in the Controller.
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