大约有 45,000 项符合查询结果（耗时：0.0497秒） [XML]
What are database normal forms and can you give examples? [closed]
...ontain only one piece of information, and there can be no duplicate rows.
2NF and 3NF are all about being dependent on the primary key. Recall that a primary key can be made up of multiple columns. As Chris said in his response:
The data depends on the key [1NF], the whole key [2NF] and nothing bu...
Visual Studio debugging/loading very slow
... they load slow, they'll always load slow after that. I could be waiting 1-2 minutes or more.
52 Answers
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Difference between natural join and inner join
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253
One significant difference between INNER JOIN and NATURAL JOIN is the number of columns return...
搭建高可用mongodb集群（二）—— 副本集 - 大数据 & AI - 清泛网 - 专注C/...
...，那我们也按照这个数量配置测试。
1、准备两台机器 192.168.1.136、192.168.1.137、192.168.1.138。 192.168.1.136 当作副本集主节点，192.168.1.137、192.168.1.138作为副本集副本节点。
2、分别在每台机器上建立mongodb副本集测试文件夹
#存...
Delete the first three rows of a dataframe in pandas
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281
Use iloc:
df = df.iloc[3:]
will give you a new df without the first three rows.
...
How to delete items from a dictionary while iterating over it?
...ionary while iterating over it:
>>> mydict = {'one': 1, 'two': 2, 'three': 3, 'four': 4}
>>> for k, v in mydict.iteritems():
... if k == 'two':
... del mydict[k]
...
------------------------------------------------------------
Traceback (most recent call last):
File ...
What is a lambda expression in C++11?
...o write something like the following, to keep the functor local:
void func2(std::vector<int>& v) {
struct {
void operator()(int) {
// do something
}
} f;
std::for_each(v.begin(), v.end(), f);
}
however this is not allowed, f cannot be passed to a template function i...
How to get multiple select box values using jQuery?
...
Michael B.
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answered Jul 14 '10 at 5:09
Pranay RanaPranay ...
CORS: Cannot use wildcard in Access-Control-Allow-Origin when credentials flag is true
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257
This is a part of security, you cannot do that. If you want to allow credentials then your Acc...
Accessing bash command line args $@ vs $*
...rs are quoted. Let me illustrate the differences:
$ set -- "arg 1" "arg 2" "arg 3"
$ for word in $*; do echo "$word"; done
arg
1
arg
2
arg
3
$ for word in $@; do echo "$word"; done
arg
1
arg
2
arg
3
$ for word in "$*"; do echo "$word"; done
arg 1 arg 2 arg 3
$ for word in "$@"; do echo "$...