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What is the difference between varchar and nvarchar?
...g from years ago!) so if the database field is VARCHAR it forces Oracle to convert between character sets on every read or write, not so good. Using NVARCHAR avoids the conversion.
Bottom line: Use NVARCHAR! It avoids limitations and dependencies, is fine for storage space, and usually best for per...
How to make execution pause, sleep, wait for X seconds in R?
...
See help(Sys.sleep).
For example, from ?Sys.sleep
testit <- function(x)
{
p1 <- proc.time()
Sys.sleep(x)
proc.time() - p1 # The cpu usage should be negligible
}
testit(3.7)
Yielding
> testit(3.7)
user sys...
Get all table names of a particular database by SQL query?
...
Stolen from here:
USE YOURDBNAME
GO
SELECT *
FROM sys.Tables
GO
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How do I check if a string is unicode or ascii?
... of the type, instead of comparing the type itself. Here's an example:
# convert bytes (python 3) or unicode (python 2) to str
if str(type(s)) == "<class 'bytes'>":
# only possible in Python 3
s = s.decode('ascii') # or s = str(s)[2:-1]
elif str(type(s)) == "<type 'unicode'>"...
bpftrace教程【官方】 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...列 DTrace Tutorial。
1. 列出所有探针
bpftrace -l 'tracepoint:syscalls:sys_enter_*'
"bpftrace -l" 列出所有探测点，并且可以添加搜索项。
探针是用于捕获事件数据的检测点。
提供的搜索词支持通配符如*/?
"bpftrace -l" 也可以通过管道...
How to create a new database after initally installing oracle database 11g Express Edition?
...ersion 3.0. This section assumes that SQL Developer is installed on
your system, and shows how to start it and connect to Oracle Database
XE. If SQL Developer is not installed on your system, see Oracle
Database SQL Developer User's Guide for installation instructions.
Note:
For the ...
How do I compare version numbers in Python?
...ys sort before valid versions.
Note: packaging has recently been vendored into setuptools.
An ancient alternative still used by a lot of software is distutils.version, built in but undocumented and conformant only to the superseded PEP 386;
>>> from distutils.version import LooseVersio...
Determine path of the executing script
...a simple solution for the problem. This command:
script.dir <- dirname(sys.frame(1)$ofile)
returns the path of the current script file. It works after the script was saved.
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How to overwrite the previous print to stdout in python?
...has. Remember to initialize curses with something like curses.setupterm(fd=sys.stdout.fileno()), and use sys.stdout.isatty() to make sure your output isn't being redirected to a file. See code.activestate.com/recipes/475116 for a full Python module with cursor control and color support.
...
What's the main difference between int.Parse() and Convert.ToInt32
...ne-grained control over the situation when the user enters invalid input.
Convert.ToInt32() takes an object as its argument. (See Chris S's answer for how it works)
Convert.ToInt32() also does not throw ArgumentNullException when its argument is null the way Int32.Parse() does. That also means tha...