Unique name and namespace

Unique name and namespace

1. The oracle database has multiple namespaces,

Distribution: USER, ROLE, and public synonym are in the same namespace.

Table, view, sequence, private synonym and user-defined type objects are in the same space.

The index has its own namespace and the constraint has its own namespace.

That is, the table name and index. The constraint can have the same name but cannot have the same name as view and sequence.

What is the definition of namespace in C?

Classes in C # are organized using namespaces. A namespace provides a way to logically organize classes to prevent name conflicts.
Namespace Declaration
Use the namespace keyword to declare a namespace. This namespace range allows you to organize code and provides you with a method to create a globally unique type.
Namespace name
{
Type Definition
}
In the namespace, you can declare classes, interfaces, structures, enumerations, and delegate namespaces.

If the namespace is not explicitly declared, the default namespace is created. The default namespace (sometimes called a global namespace ). Any identifier in the global namespace can be used in the namespace.

A namespace declaration can be used as a top-level declaration in a compilation unit. When a namespace declaration is used as a top-level declaration in a compilation unit, the namespace becomes a member of the global namespace.

When a namespace declaration appears in another namespace declaration, the internal namespace becomes a member of the external namespace that contains it.

In either case, a namespace name must be unique within its namespace. The namespace is implicitly public and cannot contain any access modifiers in The namespace declaration.

Nested namespace
The namespace is declared in the namespace declaration, and each namespace is separated.
For example:
Namespace N1.N2
{
Class {}
Class B {}
}
In terms of semantics, it is equivalent
Namespace N1
{
Namespace N2
{
Class {}
Class B {}
}
}

Reference class
When referencing a class, you can use a fully qualified name to define the reference class (before the class name, add the namespace name) to prevent name conflicts.
The using command is used to import names of other namespaces and types, instead of using qualified names.

Using command
The using alias command enables an alias for a namespace or type.
The using namespace command is used to import a namespace type member.

(1) The using namespace command imports the types contained in a namespace into the compilation unit or namespace body, this allows you to directly use these imported identifiers without the need to add their names.
For example:
Namespace N1.N2
{
Class {}
}
Namespace N3
{
Using N1.N2;
Class B
{
Public static void Main ()
{
A a = new ();
}
}
}
In the above example, the N1.N2 type members are directly available in the N3 namespace and do not need to be fully qualified.

(2) The using namespace command imports the types contained in a given namespace, but note that it does not import nested namespaces.
Example:
Namespace N1.N2
{
Class {}
}
Namespace N3
{
Using N1;
Class B
{
Public static void Main ()
{... Remaining full text>

Non-mainstream Personality Space name

When you stick your pillow, say "3 seconds" at night)
Your eyes have been reached
Why care? Why?
-You are the man she cherishes.
Messy and Russian
Lies and sounds so cute d.
"Zookeeper zhihan 1. zookeeper funeral
Alimail _ is infatuated with the high heels.
Bloom of sunflower
When you stick your pillow, say "3 seconds" at night)
Nl is the Miss in my heart
Childlike Innocence, my only show off
Night, stranded my love for you
Lonely Heart ■ never changed
The black eyes de 'sorrow ﹌
The hacker is dragging and dropping the hacker
Initially, back to the original
Look up at the remaining light in the midsummer sky
Each section has a kind of comprehension.
The memory for memory is just blank.
The ink is messy and the paper is miserable.
Who should I watch if I lose my strength and weakness?
The butterfly is drunk and withered
(I will find) road signs of life
You can't afford it
Fantasies, our impossible future
The arrow of Cupid you ordered has been issued
Cofa is not lonely, It is Spring Festival
We will be happy in the future
Who reminds me of the memories?
Just a few days ago
The most beautiful trace of memory is called memories.
Sorry, I'm proud you never had it.
Crazy and happy
There is a kind of persistence that is irreplaceable.
Giving you sunshine warmth
The period of life that everyone embraces is perfunctory.
I am a future you cannot afford.
I give you the freedom you want
A person can smile.
The sadness in the black eyes
I will shoulder your happiness
. Smile
Melancholy is something you cannot imitate
Let the past, let the future come
Last. Draw the greatest ending
I have nothing to ask
You are the past that I will never forget
Don't let me go without you
I would like to be a stranger in your eyes
∞ Weak temperament in the bones of the space name │ the most life-saving money of the enchanting and charming women