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Can I have multiple primary keys in a single table?
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Both Primary Key & Alternate keys can be Compound keys
Sources:
https://en.wikipedia.org/wiki/Superkey
https://en.wikipedia.org/wiki/Candidate_key
https://en.wikipedia.org/wiki/Primary_key
https://en.wikipedia.org/wiki/Compound_key
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How do I determine the current operating system with Node.js
...og(os.platform()); // "win32"
You can read it's full documentation here: https://nodejs.org/api/os.html#os_os_type
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Removing all empty elements from a hash / YAML?
...ct!
h = { a: 1, b: false, c: nil }
h.compact! #=> { a: 1, b: false }
https://ruby-doc.org/core-2.4.0/Hash.html#method-i-compact-21
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How do I commit only some files?
...eUploader: {
brandingHtml: "Powered by \u003ca href=\"https://imgur.com/\"\u003e\u003csvg class=\"svg-icon\" width=\"50\" height=\"18\" viewBox=\"0 0 50 18\" fill=\"none\" xmlns=\"http://www.w3.org/2000/svg\"\u003e\u003cpath d=\"M46.1709 9.17788C46.1709 8.26454 46.2665 7.94324 4...
html select only one checkbox in a group
...;
} else {
$box.prop("checked", false);
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div>
<h3>Fruits</h3>
<label>
<input type="checkbox" class="radio" value="1" name="fooby[1][]" /...
How do I use Java to read from a file that is actively being written to?
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There are a Open Source Java Graphic Tail that does this.
https://stackoverflow.com/a/559146/1255493
public void run() {
try {
while (_running) {
Thread.sleep(_updateInterval);
long len = _file.length();
if (len < _filePointer) {
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Scraping html tables into R data frames using the XML package
...rter try:
library(XML)
library(RCurl)
library(rlist)
theurl <- getURL("https://en.wikipedia.org/wiki/Brazil_national_football_team",.opts = list(ssl.verifypeer = FALSE) )
tables <- readHTMLTable(theurl)
tables <- list.clean(tables, fun = is.null, recursive = FALSE)
n.rows <- unlist(lapp...
When deleting remote git branch “error: unable to push to unqualified destination”
... went to this discussion, however I couldn't solve the problem until I saw https://stackoverflow.com/a/32147743/4209849.
which simply add a tip on distinguishing origin/my-branch-name and my-branch-name.
To be specific, I should use:
git push origin :my_remote_branch
instead of
git push orig...
How can I autoformat/indent C code in vim?
... lets you format your buffer (or buffer selections) with a single command: https://github.com/Chiel92/vim-autoformat. It uses external format programs for that, with a fallback to vim's indentation functionality.
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MQTT与TCP的区别 - 创客硬件开发 - 清泛IT社区，为创新赋能！
...机制，通知相应topic的订阅者客户端已经离线了。7. 正如https之于http，mqtts支持TLS安全，保证数据传输过程的安全性。8. mqtt协议轻巧、简单，容易实现，mqtt客户端哪怕在单片机中也可以运行。这一点在物联网应用中挺重要的，因...