大约有 47,000 项符合查询结果（耗时：0.0213秒） [XML]
How to use DISTINCT and ORDER BY in same SELECT statement?
...
The problem is that the columns used in the ORDER BY aren't specified in the DISTINCT. To do this, you need to use an aggregate function to sort on, and use a GROUP BY to make the DISTINCT work.
Try something like this:
SELECT DISTINCT Category, MAX(CreationDate)
FR...
Is there a software-engineering methodology for functional programming? [closed]
...ere are some parallels:
Many OO "design patterns" are captured as higher-order functions. For example, the Visitor pattern is known in the functional world as a "fold" (or if you are a pointy-headed theorist, a "catamorphism"). In functional languages, data types are mostly trees or tuples, and ...
Setting environment variables via launchd.conf no longer works in OS X Yosemite/El Capitan/macOS Sie
...environment file - just relaunch your application
Issues / problems:
In order your env variables were correctly taken by applications after system reboot you will need:
either login twice: login => logout => login
or close & re-open applications manually, where env variables should be...
How to extract year and month from date in PostgreSQL without using to_char() function?
...t to select sql:
SELECT "year-month" from table group by "year-month" AND order by date , where
year-month - format for date "1978-01","1923-12".
select to_char of couse work , but not "right" order:
...
Using union and order by clause in mysql
I want to use order by with union in mysql query.
I am fetching different types of record based on different criteria from a table based on distance for a search on my site.
The first select query returns data related to the exact place search .
The 2nd select query returns data related to distance ...
How to enable mod_rewrite for Apache 2.2
...
In order to use mod_rewrite you can type the following command in the terminal:
sudo a2enmod rewrite
Restart apache2 after
sudo /etc/init.d/apache2 restart
or
sudo service apache2 restart
or as per new unified System Co...
Proper way to use **kwargs in Python
...e a default value. kwargs is nice because you can submit your args in any order you choose. Positional arguments don't give you that freedom.
– Kekoa
Jul 8 '09 at 14:57
95
...
Why does the C++ STL not provide any “tree” containers?
...antees log(n) insertion/deletion/lookup (and containing elements in sorted order). This is all map is used for and is implemented (usually) as a red/black tree. A red/black tree makes sure that the tree is balanced. So the depth of the tree is directly related to the number of elements in the tree.
...
Advantage of creating a generic repository vs. specific repository for each object?
... for users.Where(u=>u.HasPurchasedAnything) instead of users.Join(x=>Orders, something something, I dont know linq).Where(order=>order.Status==1).Join(x=>x.products).Where(x.... etc etc etc.... blah blah blah
– Arnis Lapsa
Oct 7 '11 at 17:43
...
What is a plain English explanation of “Big O” notation?
... on comparison operations (comparing two nodes to determine their relative ordering). This assumes that comparison is expensive. But what if the comparison is cheap but swapping is expensive? It changes the comparison; and
complexity: if it takes me one second to sort 10,000 elements, how long wi...