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Database Engines and ANSI SQL Compliance

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I've been searching for half an hour and can't find any resources stating what level of the SQL ANSI standard is supported on various database engines. It looks like some level of support is provided by most engines, but I'd like to know exactly what level is officially supported. I'm primarily interested in MySQL, PostgreSQL, SQL Server, and Oracle. EDIT: PostgreSQL has a great page on compliance, exactly what I was looking for regarding the other engines: http://www.postgresql.org/docs/current/interactive/features.html these might help a little: Comparison of different SQL implementations

Should I learn XML 1.0 or XML 1.1?

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I know that a well-formed XML 1.1 is not necessarily a well-formed XML 1.0 and vice-versa. I want to learn xml formally and i was wondering whether i should learn XML 1.0 or XML 1.1? I mean would it be more effective to learn XML 1.0 or would it be more effective to learn XML 1.1? I mean of course I know its best to read them both.. but i really only have the time to read one of them, so which would be "better" (more useful to me, me as in the average programmer)? alexbrn Unless you have a specific requirement to work with XML 1.1 (which is very rare), you should read the XML 1.0

Where can I get free specifications of JPEG/JFIF/EXIF/etc?

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I want to make a tool for myself (and maybe others if it comes out good) for low level inspection/modification of JPEG files. Sort of like TweakPNG , but for JPEGs. So far I haven't found any tool that does this. In order to do that I need to read all the relevant specifications. Unfortunately the official ones are pretty costly , so I'm looking for alternate sources. Is there anything you can recommend which covers as much ground as possible? To answer my own question: Part 1 can be downloaded from the W3 page and the corrigendum (which contains only patent information) from the ITU page .

Constant array types in C, flaw in standard?

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问题 Paragraph 6.7.3.8 of the C99 spec states If the speciﬁcation of an array type includes any type qualiﬁers, the element type is so-qualiﬁed, not the array type. If the speciﬁcation of a function type includes any type qualiﬁers, the behavior is undeﬁned. In the rationale (logical page 87, physical page 94), an example of casting a flat pointer to a (variable length) array pointer is given. void g(double *ap, int n) { double (*a)[n] = (double (*)[n]) ap; /* ... */ a[1][2] /* ... */ } Certainly

How to interpret “Connection: keep-alive, close”?

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From what I understand, a HTTP connection could either be keep-alive or close . I sent a HTTP request to a server: GET /page1/ HTTP/1.1 Host: server.com Connection: keep-alive And it responded with: HTTP/1.1 200 OK Connection: keep-alive, close Essentially, I believe the server is bugged because a response like keep-alive, close is ambiguous. However, as the receiver , how should we handle such a message? Should we interpret this header value as keep-alive or close ? TL; DR: Chrome interprets this response header as keep-alive and maintain a peristent connection while Firefox closes each

Why is pow(-infinity, positive non-integer) +infinity?

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问题 C99 annex F (IEEE floating point support) says this: pow(−∞, y) returns +∞ for y > 0 and not an odd integer. But, say, (−∞) 0.5 actually has the imaginary values ±∞i, not +∞. C99’s own sqrt(−∞) returns a NaN and generates a domain error as expected. Why then is pow required to return +∞? (Most other languages use the C library directly or, like Python in this case, copy the behaviour required of it by standards, so in practice this affects more than just C99.) 回答1: For odd integer y , it

What's the difference between “dead code” and “unreachable code”?

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问题 I thought those terms where synonymous, but a note in MISRA regarding dead code indicates this to be wrong? What's the difference? Is one a subset of the other? 回答1: Dead code - code that is executed but redundant, either the results were never used or adds nothing to the rest of the program. Wastes CPU performance. function(){ // dead code since it's calculated but not saved or used anywhere a + b; } Unreachable code - code that will never be reached regardless of logic flow. Difference is

C++1z why not remove digraphs along with trigraphs?

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问题 C++1z will remove trigraphs. IBM heavily opposed this (here and here) so there seem to be arguments for both sides of removal/non removal. But since the decision was made to remove trigraphs, why leave digraphs? I don't see any reasons for keeping digraphs beyond the reasons to keep trigraphs (which apparently didn't weight enough to keep them). 回答1: Trigraphs are more problematic to the unaware user than digraphs. This is because they are replaced within string literals and comments. Here

Is sizeof(size_t) == sizeof(void*) always true?

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问题 Does the C99/C++11 standard guarantee that sizeof(size_t) == sizeof(void*) is always true? size_t f(void* p) { return (size_t)(p); // Is it safe? } void* f(size_t n) { return (void*)(n); // Is it safe? } 回答1: No, that is not guaranteed. Use intptr_t or uintptr_t to safely store a pointer in an integer. There are/were architectures where it makes sense for that to be false, such as the segmented DOS memory model. There the memory was structured in 64k segments - an object could never be larger

How to detect Render Mode of browser for current page?

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I know that modern browsers generally have two render mode: standard mode and quirk mode. The browser detects the heading DocType. The question is how to detect render mode of current page at runtime. Is there any Firebug tool to do that? Before IE8: alert('Page was rendered in ' + ((document.compatMode == 'CSS1Compat') ? 'Standards' : 'Quirks') + ' Mode.'); For IE8: var vMode = document.documentMode; var rMode = 'IE5 Quirks Mode'; if(vMode == 8){ rMode = 'IE8 Standards Mode'; } else if(vMode == 7){ rMode = 'IE7 Strict Mode'; } alert('Rendering in: ' + rMode); Be aware that to gain the