大约有 21,000 项符合查询结果（耗时：0.0303秒） [XML]
NOT IN vs NOT EXISTS
...
Actually, I believe this would be the fastest:
SELECT ProductID, ProductName
FROM Northwind..Products p
outer join Northwind..[Order Details] od on p.ProductId = od.ProductId)
WHERE od.ProductId is null
...
Deleting elements from std::set while iterating
... a monster beyond taming, and since there is no unique implementation (and test suites, if any, apparently do not cover such obvious cases as deleting elements in a loop), that makes the STL a shiny brittle toy that can go up with a bang when you look at it sideways.
– kuroi ne...
Select random row from a sqlite table
...0, count). MAX is used to handle a case with empty table.
Here are simple test results on a table with 16k rows:
sqlite> .timer on
sqlite> select count(*) from payment;
16049
Run Time: real 0.000 user 0.000140 sys 0.000117
sqlite> select payment_id from payment limit 1 offset abs(random(...
Difference between open and codecs.open in Python
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In Python 2 there are unicode strings and bytestrings. If you just use bytestrings, you can read/write to a file opened with open() just fine. After all, the strings are just bytes.
The problem comes when, say, you have a unicode string and you do the following:
>...
What does the [Flags] Enum Attribute mean in C#?
... You cannot use the None enumerated constant in a bitwise AND operation to test for a flag because the result is always zero. However, you can perform a logical, not a bitwise, comparison between the numeric value and the None enumerated constant to determine whether any bits in the numeric value ar...
How to refresh Android listview?
...ntation on notifyDataSetChanged(). To much in android is left to black box testing.
– Anderson
Apr 13 '14 at 11:44
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What's the difference between .so, .la and .a library files?
....
Static pro: The user always uses the version of the library that you've tested with your application, so there shouldn't be any surprising compatibility problems.
Static con: If a problem is fixed in a library, you need to redistribute your application to take advantage of it. However, unless it...
Rails check if yield :area is defined in content_for
...stance_variable_defined?(content_var_name) is a bit neater than instead of testing whether it is nil. Second bigger point, the content_for instance variable is deprecated so your solution is not future proof
– Dave Nolan
Jan 23 '09 at 22:51
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Seedable JavaScript random number generator
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If you want to use a better RNG, try the Mersenne Twister. It is a well tested and fairly robust RNG with a huge orbit and excellent performance.
EDIT: I really should be correct and refer to this as a Pseudo Random Number Generator or PRNG.
"Anyone who uses arithmetic methods to produce ran...
Why JSF calls getters multiple times
...fault:
gmapsAutoComplete = false;
break;
}
}
Test results: PageNavigationController.getGmapsAutoComplete() is no longer a HOT SPOT in Java Visual VM (doesn't even show up anymore)
Sharing this topic, since many of the expert users have advised junior JSF developers to ...