Understand several concepts of Oracle

I learned several databases like mssqlserver、sqlite etc. , Some basic logical structures 、 The physical structure is similar , But in contact oracle When , I'm still confused about some concepts , Here is a summary of several differences in the learning process ：
1、 After creating the user , The system will also create a scheme with the same name , The user has management permission for the database object under the scheme with the same name , At the same time, the system will create a default profile of the relevant vehicle （ Contains a set of constraints and configuration items , You can limit the resources that users are allowed to use ）;

2、 When you create a user , You need to specify the user's default table space and temporary table space ;

3、 Created different users , The system also creates different schemes , But you can specify the same tablespace for different users ;

4、 A tablespace is a logical storage unit . You can add one or more data files to a tablespace ;
5、 Create data objects in the scheme , The physical space in which database objects are actually stored is the table space by default   ;

6、 Multiple schemes can share a table space ;
7、oracle Sequence in

The function of sequence is to automatically generate integer values , As the value of the identification field in the table .

7.1、 Create sequence ：

Createsequence userman.user_s

Minvalue 1 The minimum value of the sequence is 1

Nomaxvalue The sequence has no maximum limit

Start with 1 The initial value of the sequence is 1

Increment by 1 The sequence interval is 1

Nocycle No cyclic value

Cache 20 Tell the cache to 20

7.2、 Usage sequence

The same sequence generator can be used for one or more tables , The generated serial number can be used to generate a unique primary key

User_s.nextval

Eg:Insertinto userman.users(user_id,user_name)values(userman.user_s.nextval,'newuser')

8、MGMT_user.make_em_user(' user name ')

Configure that the specified user can log in OEM