大约有 48,000 项符合查询结果（耗时：0.1254秒） [XML]
Sort rows in data.table in decreasing order on string key `order(-x,v)` gives error on data.table 1.
...
Update
data.table v1.9.6+ now supports OP's original attempt and the following answer is no longer necessary.
You can use DT[order(-rank(x), y)].
x y v
1: c 1 7
2: c 3 8
3: c 6 9
4: b 1 1
5: b 3 2
6: b 6 3
7: a 1 4
8: a 3 5
9: a 6 6
...
'is' versus try cast with null check
...// only one cast
if (myObjRef != null)
{
// myObjRef is already MyType and doesn't need to be cast again
...
}
C# 7.0 supports a more compact syntax using pattern matching:
if (myObj.myProp is MyType myObjRef)
{
...
}
...
How to display the function, procedure, triggers source code in postgresql?
How to print functions and triggers sourcecode in postgresql? please let me know if any one know the query to display the function, triggers source code.
...
Remove last character from C++ string
...is to use the function that is intended for this task, it's called erase() and the code is: st.erase(st.size()-1). This would be called a "mutating version".
– Czarek Tomczak
Jan 19 '13 at 14:46
...
How can I make a time delay in Python? [duplicate]
...l... it'll print less frequently than that, because it takes time to print and handle all the buffers that entails (possibly doing a kernel context switch), and to register the alarm signal, but... yeah. A little under once per minute.
– Parthian Shot
Jun 17 '1...
Why does Oracle 9i treat an empty string as NULL?
..., but that doesn't do much to tell me why this is the case. As I understand the SQL specifications, ' ' is not the same as NULL -- one is a valid datum, and the other is indicating the absence of that same information.
...
How do I check if a variable exists in a list in BASH
...amp; echo 'yes' || echo 'no'. it's correct assuming space is the separator and $x doesn't contain space
– Tianren Liu
Apr 5 '16 at 21:47
...
What's the difference between F5 refresh and Shift+F5 in Google Chrome browser?
What's the difference between F5 refresh and SHIFT + F5 in Google Chrome browser?
3 Answers
...
How to get all possible combinations of a list’s elements?
I have a list with 15 numbers in, and I need to write some code that produces all 32,768 combinations of those numbers.
27...
Unable to import a module that is definitely installed
...
I have run into this many times and I think I just discovered the reason: umask is passed through sudo, so if your personal umask is tight and you use sudo for the install, the files and directories will be over-restricted. If you simply su first and then...