6. The six modes of the Oracle Learning Starter Series

Six of the Oracle Learning Primer series

Mode

We learned the database structure, memory structure and process in Oracle database. The length of the toad feels too much. This time to take a rest, each note should not be too much, or different from the book.

We have to make sure that every record we make can be fully improved.

The last time we took a holistic grasp of the Oracle system architecture, this time we will cover the full details of the Oracle database.

This time, start with the schema object.

Old rules Let's start with two questions:

A) What's the mode

b) Why need

To figure out the two problems.

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Public Number: Hoptoad

Welcome to communicate with all

1 Schema Schema

Before learning the schema object, you must first talk about the user's concept.

We know that when we create the database, I'm going to let me enter the SYS user and the system user's password, which are two users who are systems administrators.

These two accounts because of the power is very large, so generally after the creation of the database, will create some users themselves, such as: Xiaoming,xiaohong,xiaogang and so on. These are the users we create, and what is the relationship to the pattern?

The definition of a pattern is this, schema, schema, which refers to a collection of database objects belonging to a particular user.

So, the definition of the schema is based on the user, no real users have no mode of saying. It's just that. Very many Oracle technicians replace users and patterns, although they are different things.

The general reality is this. When we deploy a database application, we use a lot of objects, such as tables, indexes, triggers, constraints, and so on, and these objects end up being attributed to a user. For example Xiaoming. Then we have a pattern called xiaoming, also called schema. A pattern is a logical structure.

Oracle creates a pattern with the same name at the same time that it creates a user. So the schema and the user are one by one corresponding.

When we visit the database, we sometimes need to specify the schema, for example, select * from Scott.emp;

This is to visit the EMP table in the Scott mode, assuming that without Scott, the pattern is to access the schema of the user's default schema.

This is Oracle's users and schemas, user and schema.

Finally figuring out what the schema is, let's say why the schema is needed.

Keep going.

2 Why mode is required

There are so many things I don't just need to know what the concept is, but also why it's needed.

So we'll remember more. and generate interest. will also prompt us to make changes and innovate.

Why need the mode, we know that users need password talent landing, and the mode and the user is one by one corresponding, then to, this is in security considerations.

Think of the user Xiao Ming has a watch called wages, Red also has a watch called wages, their tables belong to their own schema. Suppose Xiaoming didn't visit the permissions of the Little red schema. So Xiao Ming is not able to see the small red salary table, Little Red also the same. Here we need to know that access to other modes is required.

In addition to security, the other aspect is the overall management aspect.

If there is no schema, Little Red has a salary table. Xiao Ming A salary table, tomorrow came a small just also a salary table that's not a mess.

There is a schema, it is convenient, the small red salary table belongs to the small red this schema. (Suppose you say their payroll is their own user, that's right, it's just that the idea of refining it is not the schema concept?) ）

This note is very comfortable, see in the next article.

6. The six modes of the Oracle Learning Starter Series