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Cannot add or update a child row: a foreign key constraint fails
table 1
24 Answers
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How to write a simple Html.DropDownListFor()?
In ASP.NET MVC 2, I'd like to write a very simple dropdown list which gives static options. For example I'd like to provide choices between "Red", "Blue", and "Green".
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Hash function that produces short hashes?
Is there a way of encryption that can take a string of any length and produce a sub-10-character hash? I want to produce reasonably unique ID's but based on message contents, rather than randomly.
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What is the equivalent of the C# 'var' keyword in Java?
One use of the var keyword in C# is implicit type declaration. What is the Java equivalent syntax for var ?
15 Answers
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Can I set the height of a div based on a percentage-based width? [duplicate]
Let's say I've got a div that has a width of 50% of the body. How do I make its height equal to that value? So that when the browser window is 1000px wide, the div's height and width are both 500px.
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Check if a row exists, otherwise insert
I need to write a T-SQL stored procedure that updates a row in a table. If the row doesn't exist, insert it. All this steps wrapped by a transaction.
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What is the difference between print and puts?
For example in this line of code I wrote, print and puts produce different results.
6 Answers
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Can I use a hash sign (#) for commenting in PHP?
I have never, ever, seen a PHP file using hashes ( # ) for commenting. But today I realized that I actually can! I'm assuming there's a reason why everybody uses // instead though, so here I am.
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Enums and Constants. Which to use when?
I was doing some reading on enums and find them very similar to declaring constants. How would I know when to use a constant rather than an enum or vice versa. What are some of the advantages of using enums?
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How important is the order of columns in indexes?
I've heard that you should put columns that will be the most selective at the beginning of the index declaration. Example:
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