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, and the length of toad felt much more. This time to take a rest, each note should not be too much, or what is the difference between books. We have to make sure that every record we make can reap all the gains.

The last time we took a general overview of the Oracle system architecture, this time we will cover the specific aspects of Oracle database. This time, start with the schema object.

The usual, first two questions:

A) What's the mode

b) Why do I need

To figure out the two problems.

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Public Number: Hoptoad

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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 enter the password for the SYS user and system user, which is the system administrator for the two users. 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 such that a schema, schema, refers to a collection of database objects belonging to a particular user. So, the definition of the schema is based on the user, no user has no mode of saying. However, many Oracle technicians replace users and patterns, although they are different things.

The general reality is that when we deploy a database application, we use a lot of objects, such as tables, indexes, triggers, constraints, and so on, and these objects are ultimately to be attributed to a user, such as xiaoming. Then we have a pattern called xiaoming, also called schema. A pattern is a logical structure.

Oracle creates a user with a schema with the same name, so the schema and the user are one by one corresponding.

We sometimes need to specify access to the schema when accessing the database, such as SELECT * from Scott.emp;

This is the EMP table in the Scott mode, and if you don't add Scott, the schema is access to 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 a pattern is needed

A lot of things I don't just want to know what the concept is, but also why you need it. This way we will remember to be more secure, and to generate interest, but also to make us change and innovate.

Why need a pattern, we know that users need a password to log in, 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. If Xiao Ming does not have access to the small red schema, then Xiao Ming is not able to see the small red salary table, Xiao Red also the same. Here we need to know that access to other schemas requires permission.

In addition to security, there is one aspect of overall management. 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. (If you say their payroll is their own user, that's true, but is this the idea of a schema?) ）

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

Six modes of the Oracle Learning Starter Series