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Can a foreign key be NULL and/or duplicate?
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Short answer: Yes, it can be NULL or duplicate.
I want to explain why a foreign key might need to be null or might need to be unique or not unique. First remember a Foreign key simply requires that the value in that field must exist first in a...
Java HTTPS client certificate authentication
I'm fairly new to HTTPS/SSL/TLS and I'm a bit confused over what exactly the clients are supposed to present when authenticating with certificates.
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Which HTML elements can receive focus?
I'm looking for a definitive list of HTML elements which are allowed to take focus, i.e. which elements will be put into focus when focus() is called on them?
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Can every recursion be converted into iteration?
A reddit thread brought up an apparently interesting question:
17 Answers
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C: What is the difference between ++i and i++?
...eing incremented.
i = 1;
j = i++;
(i is 2, j is 1)
For a for loop, either works. ++i seems more common, perhaps because that is what is used in K&R.
In any case, follow the guideline "prefer ++i over i++" and you won't go wrong.
There's a couple of comments regarding the efficiency of +...
How to make a whole 'div' clickable in html and css without JavaScript? [duplicate]
I want to make it so that a whole div is clickable and links to another page when clicked without JavaScript and with valid code/markup.
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Error handling in Bash
What is your favorite method to handle errors in Bash?
The best example of handling errors I have found on the web was written by William Shotts, Jr at http://www.linuxcommand.org .
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Creating a blurring overlay view
...sic app of the new iOS, we can see an album cover behind a view that blurs it.
25 Answers
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What's wrong with nullable columns in composite primary keys?
ORACLE does not permit NULL values in any of the columns that comprise a primary key. It appears that the same is true of most other "enterprise-level" systems.
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Post data to JsonP
Is it possible to post data to JsonP? Or does all data have to be passed in the querystring as a GET request?
7 Answers
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