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Does a valid XML file require an XML declaration?
... It even goes on to state that if the declaration is absent, that automatically implies the document is an XML 1.0 document.
Note that in an XML Declaration the encoding and standalone are both optional. Only the version is mandatory. Also, these are not attributes, so if they are present they must...
Unique constraint that allows empty values in MySQL
...reference (version 5.5).
A UNIQUE index creates a constraint such that all values in the index must be distinct. An error occurs if you try to add a new row with a key value that matches an existing row. For all engines, a UNIQUE index allows multiple NULL values for columns that can contain NU...
When is finally run if you throw an exception from the catch block?
In the above block when is the finally block called? Before the throwing of e or is finally called and then catch?
7 Answer...
How do I scroll to an element within an overflowed Div?
... a good way to scroll to item #10, and then item #20? I know the height of all the items.
7 Answers
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Where can I find the Java SDK in Linux after installing it?
I installed JDK using apt-get install but I don't know where my jdk folder is. I need to set the path for that. Does any one have a clue on the location?
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What is the maximum possible length of a query string?
...::Daemon module will encounter a 16,384 byte limit on the combined size of all HTTP request headers. This does not include POST-method form data, file uploads, etc., but it does include the URL. In practice this resulted in a 413 error when a URL was significantly longer than 8,000 characters. This ...
Capturing mobile phone traffic on Wireshark
... suggestions:
For Android phones, any network: Root your phone, then install tcpdump on it. This app is a tcpdump wrapper that will install tcpdump and enable you to start captures using a GUI. Tip: You will need to make sure you supply the right interface name for the capture and this varies from...
Collisions when generating UUIDs in JavaScript?
...rom Math.random(). For some browsers the entropy is as low as just 41 bits all together. Calling Math.random() multiple times won't raise the entropy. If you really want unique v4 UUIDs you need to use a cryptographically strong RNG that produces at least 122bit entropy per UUID generated.
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Does the join order matter in SQL?
...ssociative as long as neither predicate can be satisfied by a row in which all columns from one table are NULL, than to say that it's associative as long as the predicates don't involve IS NULL or 'a function that is related to nulls'. One can easily imagine a predicate that satisfies the former des...
Heap vs Binary Search Tree (BST)
... 1
Create worst n log(n) n
Delete worst log(n) log(n)
All average times on this table are the same as their worst times except for Insert.
*: everywhere in this answer, BST == Balanced BST, since unbalanced sucks asymptotically
**: using a trivial modification explained in thi...