大约有 45,000 项符合查询结果（耗时：0.0895秒） [XML]
difference between primary key and unique key
...cannot be NULL - e.g. MySQL adds NOT NULL
Primary Key is a unique key identifier of the record
Unique Key:
Can be more than one unique key in one table
Unique key can have NULL values
It can be a candidate key
Unique key can be NULL ; multiple rows can have NULL values and therefore may not be c...
Explain the encapsulated anonymous function syntax
...ork because it is being parsed as a FunctionDeclaration, and the name identifier of function declarations is mandatory.
When you surround it with parentheses it is evaluated as a FunctionExpression, and function expressions can be named or not.
The grammar of a FunctionDeclaration looks like this:...
Search for all files in project containing the text 'querystring' in Eclipse
...le Search" tab.
additional search options
search for resources: Ctrl + Shift + R
search for Java types: Ctrl + Shift + T
share
|
improve this answer
|
follow
...
angularjs directive call function specified in attribute and pass an argument to it
I want to create a directive that links to an attribute. The attribute specifies the function that should be called on the scope. But I also want to pass an argument to the function that is determined inside the link function.
...
How to avoid warning when introducing NAs by coercion
...t the problematic characters to NA first. For your particular problem, taRifx::destring does just that. This way if you get some other, unexpected warning out of your function, it won't be suppressed.
> library(taRifx)
> x <- as.numeric(c("1", "2", "X"))
Warning message:
NAs introduced b...
What's the difference between design patterns and architectural patterns?
...tailed explanation but I will try to sketch the differences to best of my knowledge.
Patterns are distilled commonality that you find in programs. It allows us to deconstruct a large complex structure and build using simple parts. It provides a general solution for a class of problems.
A large co...
Do you use source control for your database items? [closed]
...First get src ctrl, then think about a tool.
– ulty4life
Oct 27 '10 at 22:42
1
There's a distribu...
How can you check which options vim was compiled with?
...ction with the feature you are looking for. The code below will return a 1 if it has the feature or 0 if it does not.
:echo has('python')
For a list of features see :h +feature-list
For more information see:
:h :version
:h has(
:h feature-list
...
include external .js file in node.js app
...se has been saying var foo in top level does not create a global variable. If you want a global variable then write global.foo. but we all know globals are evil.
If you are someone who uses globals like that in a node.js project I was on I would refactor them away for as there are just so few use c...
What are paramorphisms?
...of the input and gives just the output value. It's not very efficient, but if you're interested in sheer expressivity, para gives you no more than foldr. If you use this foldr-encoded version of para, then safeTail will take linear time after all, copying the tail element by element.
So, that's it:...