大约有 47,000 项符合查询结果（耗时：0.0288秒） [XML]
SQL Inner-join with 3 tables?
...
You can do the following (I guessed on table fields,etc)
SELECT s.studentname
, s.studentid
, s.studentdesc
, h.hallname
FROM students s
INNER JOIN hallprefs hp
on s.studentid = hp.studentid
INNER JOIN halls h
on hp.hallid = h.hallid
Based on your request for ...
PowerShell script to return versions of .NET Framework on a machine?
...ame Version,Release -EA 0 |
Where { $_.PSChildName -match '^(?!S)\p{L}'} |
Select PSChildName, Version, Release
Based on the MSDN article, you could build a lookup table and return the marketing product version number for releases after 4.5:
$Lookup = @{
378389 = [version]'4.5'
378675 = [...
How to check if mysql database exists
...
SELECT SCHEMA_NAME
FROM INFORMATION_SCHEMA.SCHEMATA
WHERE SCHEMA_NAME = 'DBName'
If you just need to know if a db exists so you won't get an error when you try to create it, simply use (From here):
CREATE DATABASE IF NO...
What's the difference between a temp table and table variable in SQL Server?
...-unique indexes too.
Table variables don't participate in transactions and SELECTs are implicitly with NOLOCK. The transaction behaviour can be very helpful, for instance if you want to ROLLBACK midway through a procedure then table variables populated during that transaction will still be populated...
Map and Reduce in .NET
...ons. C# 3.5 and Linq already has it albeit under different names.
Map is Select:
Enumerable.Range(1, 10).Select(x => x + 2);
Reduce is Aggregate:
Enumerable.Range(1, 10).Aggregate(0, (acc, x) => acc + x);
Filter is Where:
Enumerable.Range(1, 10).Where(x => x % 2 == 0);
https://www...
Default filter in Django admin
...lookup, title in self.lookup_choices:
yield {
'selected': self.value() == lookup,
'query_string': cl.get_query_string({
self.parameter_name: lookup,
}, []),
'display': title,
}
def querys...
Right query to get the current number of connections in a PostgreSQL DB
...ires aren't equivalent. The equivalent version of the first one would be:
SELECT sum(numbackends) FROM pg_stat_database;
In that case, I would expect that version to be slightly faster than the second one, simply because it has fewer rows to count. But you are not likely going to be able to measu...
How to convert a selection to lowercase or uppercase in Sublime Text
I have several strings selected in a file in Sublime Text and I want to convert them all to lowercase.
5 Answers
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select、poll、epoll之间的区别总结[整理] - C/C++ - 清泛网 - 专注C/C++及内核技术
select、poll、epoll之间的区别总结[整理]select，poll，epoll都是IO多路复用的机制。I O多路复用就通过一种机制，可以监视多个描述符，一旦某个描述符就绪（一般是读就绪或者写就绪...select，poll，epoll都是IO多路复用的机制。I/O多路...
Set selected radio from radio group with a value
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With the help of the attribute selector you can select the input element with the corresponding value. Then you have to set the attribute explicitly, using .attr:
var value = 5;
$("input[name=mygroup][value=" + value + "]").attr('checked', 'checked');
...