大约有 47,000 项符合查询结果（耗时：0.0697秒） [XML]
SQL select only rows with max value on a column [duplicate]
...ou join your table to the sub-query with equality on both group-identifier and max-value-in-group:
SELECT a.id, a.rev, a.contents
FROM YourTable a
INNER JOIN (
SELECT id, MAX(rev) rev
FROM YourTable
GROUP BY id
) b ON a.id = b.id AND a.rev = b.rev
Left Joining with self, tweaking join...
How to calculate time difference in java?
...ariables won't do much good.. In this example, sure, you could invert them and take the absolute value or something. But what happens if you have midnight (00:00)?
– rj2700
Feb 20 '17 at 23:00
...
is_null($x) vs $x === null in PHP [duplicate]
PHP has two (that I know of, and three if you count isset() ) methods to determine if a value is null: is_null() and === null . I have heard, but not confirmed, that === null is faster, but in a code review someone strongly suggested that I use is_null() instead as it is specifically design...
When to use PNG or JPG in iPhone development?
...
PNG's are pixel perfect (non-lossy), and require very little extra CPU energy to display. However, large PNGs may take longer to read from storage than more compressed image formats, and thus be slower to display.
JPG's are smaller to store, but lossy (amount ...
What is the difference between hg forget and hg remove?
...
'hg forget' is just shorthand for 'hg remove -Af'. From the 'hg remove' help:
...and -Af can be used to remove files
from the next revision without
deleting them from the working
directory.
Bottom line: 'remove' deletes the file from your...
How do you add CSS with Javascript?
... { color: red; }', sheet.cssRules.length);
...on all but (naturally) IE8 and prior, which uses its own marginally-different wording:
sheet.addRule('strong', 'color: red;', -1);
There is a theoretical advantage in this compared to the createElement-set-innerHTML method, in that you don't have to...
What is the minimum valid JSON?
...a JSON text as being a serialized object or array.
This means that only {} and [] are valid, complete JSON strings in parsers and stringifiers which adhere to that standard.
However, the introduction of ECMA-404 changes that, and the updated advice can be read here. I've also written a blog post on ...
Things possible in IntelliJ that aren't possible in Eclipse?
I have heard from people who have switched either way and who swear by the one or the other.
41 Answers
...
Scala actors: receive vs react
...ives something. Once it receives something, a thread gets allocated to it, and it is initialized in it.
Now, the initialization part is important. A receiving thread is expected to return something, a reacting thread is not. So the previous stack state at the end of the last react can be, and is, w...
How to initialize all members of an array to the same value?
...s that value is 0 (in which case you can omit some part of the initializer
and the corresponding elements will be initialized to 0), there's no easy way.
Don't overlook the obvious solution, though:
int myArray[10] = { 5, 5, 5, 5, 5, 5, 5, 5, 5, 5 };
Elements with missing values will be initiali...