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Oracle 12c Enterprise Edition database can be deployed through blog post. This blog article mainly introduces the architecture of Oracle, including storage structure, memory structure and process structure. It is of great help to further study the Oracle database.

Blog outline:

I. Oracle architecture

Overview of 1.Oracle Architecture

2.Oracle server

3.Oracle storage structure

4.Oracle memory structure

5.Oracle process structure

2. Basic operation of CDB and PDB

III. User management

IV. Database authority management

5. Import test data

I. Oracle architecture

The architecture of the database refers to the composition and working process of the database, as well as the organization and management mechanism of the data in the database. To understand the architecture of the Oracle database, we must understand the main components and important concepts of the Oracle system.

Overview of 1.Oracle Architecture

The Oracle architecture consists of a series of components, as shown in the figure:

The figure shows the main components of the Oracle architecture, including instances, user processes, server processes, data files, and other files, such as parameter files, password files, and archive log files.

As you can see from the figure, instances and databases are the core components of the Oracle database architecture and the two most important concepts.

As a DBA manager, maintaining the proper operation of the instance and the database itself is the most basic skill.

(1) examples

An Oracle instance is a collection of background processes and memory structures, and you must start the instance to access the data in the database. When the Oracle instance starts, a system global area (SGA) is assigned and a series of Oracle background processes are started.

There are two types of Oracle instances:

Single-process Oracle instances use one process to perform all Oracle operations, and Oracle instances in a single-process environment allow only one user to access; multi-process Oracle instances use multiple processes to execute different parts of Oracle, with one process for each connected user; (2) Database

A database is a collection of data, which physically refers to a set of operating system files that store database information. Each database has a logical structure and a physical structure.

The physical structure refers to a set of operating system files that make up the database, which is mainly composed of three types of files, data files, control files and redo log files; the logical structure of the database refers to the logical storage structure of database data (such as table space, segment) and schema objects (such as tables, views, etc.); (3) pluggable database

Starting with the Oracle 12c release, Oracle introduced the concept of pluggable databases, which were created for cloud computing. The pluggable structure consists of a container database (CDB) and several assemblable databases (PDB). Each PDB can be used as an independent database worker application, it can contain its own data files, but all PDB share CDB control files and log files. The so-called pluggable means that PDB can be plugged into the CDB at any time like USB, and can be unplugged at any time when it is not in use. A maximum of 250 PDB can be inserted in a CDB. In PDB, seedPDB is the template PDB, which provides a template for the newly created PDB, and other PDB can be created and deleted as needed. The pluggable feature can speed up the deployment of the database, and a patch to a CDB can synchronize all updates to all PDB on it.

In versions prior to Oracle 12c, instances and databases could only be one-to-one or many-to-one, that is, only one instance could correspond to one database, or multiple instances could correspond to one database. In Oracle 12c version, through the introduction of CDB and PDB, an instance can correspond to multiple pluggable databases.

Usage scenarios for pluggable databases:

(1) many applications in the enterprise need to use Oracle database. They only use a very small amount of hardware resources, but have to create multiple instances for them.

(2) for some databases that are not very important, packaging requires a lot of effort from DBA to maintain.

(3) in order to make better use of hardware resources and reduce management overhead, it is necessary to integrate a large number of departmental applications into a few Oracle relational databases for deployment and management.

Deploying multiple databases through a centralized platform while sharing a database instance can greatly reduce the cost, that is, less instance loss and arable land storage technology.

If you need only one database in a production environment and do not want to use a pluggable database, you can uncheck the create as Container Database check box during installation and a normal database will be installed.

2.Oracle server

Oracle server is also a very important concept, which is mainly composed of strength and database files, which is often referred to as database management system (DBMS).

The composition of the Oracle server is as follows:

In addition to maintaining instance and database files, the Oracle server also starts the server process and allocates PGA when the user establishes a connection to the server.

3.Oracle storage structure

The storage structure of Oracle is divided into physical structure and logical structure, which are independent and related to each other. As shown in the figure:

The physical structure mainly describes the external storage structure of the Oracle database, that is, how to organize and manage the data in the operating system; the logical structure mainly describes the internal storage structure of the Oracle database, that is, logically describes how to organize and manage the data in the Oracle database; (1) Oracle physical structure

The physical structure is the operating system physical files used after the creation of the Oracle database. The physical files of the Oracle database are divided into the following two categories:

1) main document

(1) data file: the data file, which usually has a .dbf extension, is a file that physically stores Oracle database data.

Characteristics of data files:

Each data file is associated with only one database; a tablespace can contain one or more data files; a data file can only belong to one tablespace

(2) redo log file: the extension of the redo log file is .log, which records all changes to the data and provides a data recovery mechanism to ensure that the database is restored after a system crash or other unexpected occurrence.

In the Oracle database, redo log files are used in groups, and each redo log file group can have more than one redo log file. In the course of work, multiple redo log filegroups are recycled, and when one redo log filegroup is full, it goes to the next log filegroup. The redo log file is used to record database changes and is the user's transaction log.

(3) Control file: the control file has a .ctl extension and is a binary file. There is a lot of information stored in the control file, including the name and location of the data file and the redo log file. Control files are necessary for database startup and operation. When Oracle reads and writes data, it should look up the data file according to the information of the control file.

Because of the importance of control files, a database must have at least two control files. Oracle 12c contains two control files by default, each of which has the same content, thus avoiding the failure to start the database due to the corruption of one control file.

The following information is recorded in the control file:

Location and size of data files; location and size of redo log files; database name and creation time; log sequence number; 2) other files

Other files include parameter files, archive log files, password files, and so on.

(2) logical structure

The logical structure of the database analyzes the composition of the database from a logical point of view. The logical structure of Oracle database includes table space, segment, extent, block, schema and so on. As shown in the figure:

1) tablespace

Each Oracle database is made up of several tablespaces, and all the content created by users in the database is stored in the tablespace. A tablespace can consist of multiple data files, but a data file can only belong to one tablespace. Unlike the physical structure of data files, tablespaces belong to the logical structure of the database.

In each database, there is a tablespace called "SYSTEM", that is, the system tablespace, and there are also tablespaces such as SYSAUX, UNDO, USERS, and so on, which are created automatically when the database is created. Administrators can create custom tablespaces and assign them to specified users, or they can add and delete data files for tablespaces.

There are basically three types of tablespaces:

(1) permanent tablespaces: data that generally maintains base tables, attempts, procedures, indexes, etc. SYSTEM, SYSAUX, USERS tablespaces are installed by default

(2) temporary tablespaces: only used to save data of short-term activities in the system, such as sorted data, etc.

(3) undo tablespace: used to help roll back uncommitted transaction data. Committed data cannot be recovered here.

There is generally no need to create temporary and undo tablespaces unless they are transferred to other disks to improve performance.

The purpose of the tablespace is as follows:

Assign different tablespaces to different users and different tablespaces to different schema objects to facilitate user operation and management of schema objects; different data files can be created on different disks, which is helpful to manage disk space, improve Imax O performance, backup and restore data, etc.

Generally speaking, after completing the installation of the Oracle system and creating an Oracle instance, the Oracle system automatically tries its best to create multiple table spaces such as SYSTEM, SYSAUX, USRS and so on.

Here is a detailed description of these tablespaces:

SYSTEM tablespace: data used to store tables and data dictionaries within the Oracle system, such as table names, column names, user names, etc. It is not recommended to store user-created tables, indexes and other objects in SYSTEM tablespaces; SYSAUX tablespaces: as auxiliary tablespaces of SYSTEM, it is used to store data of users of various database tools; it is also used to store object data of various schemas, such as intelligent agent user DBSNMP, which establish corresponding objects and store them in SYSAUX tablespaces after the database is installed. USERS tablespace: usually used as a user tablespace, you can create a variety of objects, such as tables, indexes, etc.; TEMP tablespace: a special tablespace used by Oracle systems to store temporary data. For example, when sorting is needed in an operation, the Oracle system temporarily stores the sorted data in the tablespace. After the sorting process is completed, the space occupied by the sorted data can be freed, so it becomes a temporary tablespace.

In addition to the tablespaces created by default in the Oracle system, users can create multiple tablespaces based on the schema of the application system and the types of objects to be stored to distinguish between user data and system data.

Create a tablespace data definition language with the following syntax:

In grammar:

Tablespacename: the name of the table space; DATAFILE: specify one or more data files that make up the table space, separated by commas when there are multiple data files; filename: the path and name of the data file in the table space; SIZE: specify the size of the file, which can be K or M: to start or disable the automatic extension of the data file. If set to ON, it means that space is exhausted and automatically expands; if set to OFF, it is easy to see that the remaining capacity of the tablespace is 0, resulting in the situation that the data cannot be stored in the database. 4.Oracle memory structure

Memory structure is the most important part of Oracle database system, and memory is also the first factor that affects database performance.

The main contents of Oacle memory storage:

Program code; information about connected sessions, including all current active and inactive sessions; information necessary for the program to run, such as query plans; information communicated and shared between Oracle processes, such as locks

Depending on how memory is used, the memory of Oracle databases can also be divided into the following categories:

SGA: the shared memory area of the instance that is accessible to all users. Data blocks, transaction logs, data dictionary information, etc., are all stored in SGA; PGA: a class of non-shared memory dedicated to a specific server process and accessible only by that process; UGA: the area of memory that stores session state for user processes. Depending on whether the user database is configured in dedicated server mode or shared server mode, UGA can be part of SGA or PGA. It stores data for user sessions.

Focus on SGA and PGA:

(1) SGA

The SGA of the Oracle instance stores database information and is shared by multiple database processes. When the database instance starts, SGA's memory is automatically allocated. SAG is the largest area of server memory in the database, and it is also an important index that affects the performance of the database.

According to its different functions, SGA can be divided into the following parts:

1) shared pool

Shared pool is the memory area used for parsing, compiling and executing SQL and PL/SQL programs.

Shared pools consist of a library cache and a data dictionary cache:

The library cache contains the analysis code and execution plan of the recently executed SQL and PL/SQL statements; the data dictionary cache contains tables, indexes, column definitions, permission information and other database object definitions obtained from the data dictionary, and if Oracle caches these information, it undoubtedly shortens the response time of the query; 2) data buffers

The data buffer is used to store data read from disk data files for sharing by all users. When you modify the data, you should first take the data from the data file and store it in the data buffer. The modified data and the inserted data are stored in the data buffer, and the data is written to the data file only when the modification is completed and other conditions are met.

When processing a query, the Oracle server process first looks for the existence of the required data blocks in memory. If the desired block is not found in the data buffer, the server process reads the block from the data file and saves it in the buffer. When subsequent requests need to read these blocks, they can be found in memory, so these requests do not need to be read from disk, thus improving the reading speed. The size of the data buffer has a direct impact on the reading speed of the database.

3) redo log buffer

When users perform operations such as INSERT, UPDATE, DELETE, CREATE, ALTER, DROP, etc., the data changes. The changed data is written to the redo log buffer before it is written to the data cache, and the data before the change is also put into the redo log cache, so that Oracle knows which resources need to be committed and which resources need to be withdrawn when the data is recovered. The log buffer has less impact on the performance of the database than the data buffer.

4) Daichi

In SGA, a large pool is an optional buffer that the administrator can configure as needed. Large pools are also needed as buffer space in the process of large-scale input, output and backup, such as big data operation, database backup and recovery.

5) Java Pool

The Java pool is also an optional buffer in SGA, but when you install Java or use a Java program, you must set up the Java pool to compile instructions written in the Java language.

(2) PGA

PGA is not part of the instance, it contains the data and control information required by a single server process or a single background process. PGA is automatically allocated when the user process connects to the database and creates a session, and the partition retains the memory required by each user process connected to the Oracle database. After a user ends the session, the PGA is released.

5.Oracle process structure

There are several different types of processes in Oracle:

User process: starts when the database user requests to connect to the Oracle server; server process: starts when the user establishes a session and connects to the Oracle instance; background process: starts when the Oracle instance starts

The user process is a program that needs to interact with the Oracle server process. A user process is created when a database user runs an application ready to send a request to the database server. For example, when a user starts the database tool Sqlplus, the system will automatically establish a user process.

The server process is used to process requests from the user process connected to the instance. When the user establishes a connection to the database, the server process is generated. The server process communicates with the user process and requests services for the connected users. The server process interacts with the Oracle database directly to achieve the purpose of calling and returning results. The server process can handle the requests of one user process, and it can also handle the requests of multiple user processes.

In the Oracle database, in order to make the system performance better coordinate multiple users, some additional processes used in the instance system are called background processes. These background processes exist in the operating system and start automatically when the instance starts. Five of these processes must be started, or the database instance cannot be started. The five processes are:

(1) PMON (process monitoring) process

The PMON process performs resource cleanup after an unexpected disconnection to the user, including the following tasks:

Release all currently pending locks; roll back users' current transactions; release resources currently used by users; monitor server processes and other background processes and restart them in case of failure; (2) SMON (system monitoring) processes

The SMON process performs the following tasks:

Perform instance recovery when the instance is started. Instance recovery includes three steps:

(1) roll forward to recover unwritten data files but recorded in online log files

(2) Open the database so that users can log in and access the data

(3) rollback for committed transactions; organize free space for data files; release temporary periods that are no longer used; (3) DBWR (data writing) process

The DBWR process performs the following tasks:

Manage data buffers so that you can find free buffers to read data into the data file; write all modified buffer data to the data file; keep recently used blocks using the LRU algorithm in memory; optimize disk Imax O read and write by delaying writes; (4) LGWR (log write) process

The LGWR process is responsible for writing log data from the redo log buffer to the log filegroup. When the database is running, if the data is modified, the log information is generated, and the log information is first generated in the redo log buffer. This buffer operates according to the principle of "first-in, first-out". The log information satisfies a certain condition that the log data is written to the log file by the LGWR process. The system usually has multiple log files, and the log writing process writes data to the file in a circular manner.

(5) CKPT (checkpoint) process

The CKPT process is the mechanism that ensures that all modified blocks in the data buffer are written to the data file. When the checkpoint is completed, the CKPT process is responsible for updating the data file header and control file, and saving the checkpoint information to ensure the synchronization of the database log file and the data file. When the database is restored, you only need to find the last checkpoint saved by CKPT, and then you can use it to determine the starting location of the recovery data in the log file, and then re-execute the logging that followed.

(6) ARCn process

The ARCn process, the Archive Log process, is an optional process that is available only when log archiving is opened. The main role of this process is to copy full online log files to the archive directory when a log switch occurs.

2. Basic operation of CDB and PDB

Unlike previous versions of Oracle, Oracle 12c can be used as a single database or provide several pluggable PDB databases according to the needs of the enterprise. Each PDB can be maintained by a different DBA.

Here is a brief introduction to the basic maintenance of CDB and PDB:

[oracle@oracle] $sqlplus sys as sysdba / / Log in to the database as sys user SQL*Plus: Release 12.2.0.1.0 Production on Saturday November 30 15:26:41 2019Copyright (c) 1982, 2016, Oracle. All rights reserved. Enter the password: * connected to the idle routine. The SQL > startup; / / startup database ORACLE routine has been started. Total System Global Area 2466250752 bytesFixed Size 8795760 bytesVariable Size 671091088 bytesDatabase Buffers 1778384896 bytesRedo Buffers 7979008 bytes database loaded. The database is already open. SQL > show con_name; / / query the current container CON_NAME--CDB$ROOT / / indicates that SQL > show pdbs is currently under CDB / / query all containers in the database CON_ID CON_NAME OPEN MODE RESTRICTED- 2 PDB$SEED READ ONLY NO / / create PDB database template 3 ORCLPDB MOUNTED / / status is mounted (no open) SQL > alter pluggable database orclpdb open / / Open the pluggable database orclpdb under CDB / / if you have switched to PDB without opening the PDB, you can use "shutdown immediate" to close the PDB database, "startup" to start the PDB database plug-in database has changed. Switch session to PDB under SQL > alter session set container=orclpdb; / / CDB. The session has changed. SQL > show con_name; / / check again that the current location is in orclpdb CON_NAME--ORCLPDBSQL > alter session set container=cdb$root; / / back to the CDB database session has changed. SQL > show con_name;CON_NAME--CDB$ROOT

The above is the switch from CDB to PDB, and vice versa.

There are two ways to connect to the pluggable database PDB:

The first method is to log in to the CDB database first, and then switch to the PDB database. The second method is to log in directly to the PDB database when logging in.

The second method is as follows:

[oracle@oracle ~] $vim / u01/app/oracle/product/12.2.0/dbhome_1/network/admin/tnsnames.ora LISTENER_ORCL = (ADDRESS = (PROTOCOL = TCP) (HOST = oracle) (PORT = 1521) ORCL = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP) (HOST = oracle) (PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orcl))- -/ / dividing line The above does not need to be modified lzj = / / write according to the above template This name can be customized (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP) (HOST = oracle) (PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orclpdb) / / the PDB database name needs to be specified here)) [oracle@oracle ~] $sqlplus sys@lzj as sysdba / / specify the name just defined when logging in to the database: SQL*Plus: Release 12.2.0.1.0 Production on Saturday November 30 15:48:50 2019Copyright (c) 1982 2016, Oracle. All rights reserved. Enter the password: * Connect to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0-64bit ProductionSQL > show con_name; / / View for authentication CON_NAME--ORCLPDB 3. User management

When creating a new database, Oracle creates some default database users, such as SYS, SYSTEM, and so on.

A brief introduction to the users of Oracle database:

(1) SYS

SYS user is a super user in Oracle, which is mainly used to maintain system information and manage instances. All data dictionaries and views in the database are stored in the SYS schema. The data dictionary stores all the information used to manage database objects and is a very important system information in Oracle database. SYS users can only log in to the database system in the SYSOPER or SYSDBA role.

(2) SYSTEM

The SYSTEM user is the default database administrator in Oracle and has DBA privileges. This user mode stores the internal tables and views used by the Oracle management tools. Users, permissions, and storage of Oracle databases are usually managed by SYSTEM users, and it is not recommended to create user tables in SYSTEM schema. SYSTEM users cannot log in to the database system in the role of SYSOPER or SYSDBA, but can only log in in the default way (database authentication).

(3) Custom user

Oracle 12c supports the creation of custom users, which are different from previous versions due to the introduction of PDB. In CDB mode, there are two types of users: public users and local users. Public users can be used in CDB and PDB, while local users can only be used in PDB. In a CDB environment, the creation of local users is not allowed. Oracle states that when a public user is created in CDB, the user name must start with clocked #.

In general, for security reasons, different users need different access to their data tables, so different users need to be created. The CREATE USER command in Oracle is used to create a new user. Each user has a default space and a temporary tablespace. If not specified, Oracle sets USERS as the default tablespace and TEMP as the temporary tablespace.

The syntax for creating a user is as follows:

In grammar:

SQL > create user c##lzj 2 identified by 123456; / / create user user has been created. SQL > alter user c##lzj identified by 654321; / / modify user password the user has changed. SQL > drop user c##lzj cascade; / / Delete user user has been deleted. / / when deleting a user, without cascade means to delete only the user, and with cascade means to delete the user, that is, the user mode object. 4. Database rights management

Permission is the right to execute some type of SQL statement to access other user database objects. In Oracle, permissions are divided into two categories: system permissions and object permissions.

1. System permissions

System permission refers to the right to perform a system-level operation in a database, or to perform an operation on a certain class of objects. As shown in the figure:

Common system permissions are as follows:

CREATE SESSION: connect to the database; CREATE TABLE: create tables; CREATE VIEW: create views; CREATE SEQUENCE: create sequences

After a new user is created, it is preferred to grant him CREATE SESSION permission to log in to the database.

two。 Object permissions

Object permissions are the rights to perform operations on a particular schema object. As shown in the figure:

There are two ways for Oracle database users to gain permissions: ① grants permissions directly to users, and ② grants permissions to roles, which in turn grant roles to one or more users. Using roles makes it easier and more efficient to manage permissions. So the database administrator grants permissions to users by using roles, rather than directly. Many roles are predefined in Oracle database system, among which the most commonly used roles are CONNECT role, RESOURCE role, DBA role and so on.

The system predefined roles commonly used in Oracle are as follows:

CONNECT: have the permission to connect to the database; RESOURCE: have the permission to create tables, triggers, procedures, etc.; DBA: database administrator role, with the highest permissions to manage the database

Newly created users must be granted certain permissions to operate on the database.

SQL > grant connect,resource to censor granted lzj; authorization succeeded. SQL > revoke connect,resource from cantilever cancel lzj; undo successfully.

The design principles of database user security are as follows:

Database users can be divided into four categories: management, application, maintenance and backup, database users are not allowed to use sys and system users to establish database application objects, dba permissions are prohibited to ordinary users, query permissions can only be open to query users, and password changes are forced for new users when they log in to the database for the first time.

General program developers only need to grant the roles of connect and resource. Note: granting these two roles includes granting users unrestricted access to the default tablespace.

Create a user lzj in PDB mode and authorize it. Specific actions are as follows:

SQL > select name from vexpdbs; / / query all pluggable databases NAME----PDB$SEEDORCLPDBSQL > alter session set container=orclpdb / / switch to pluggable database orclpdb session has changed. SQL > show con_name; / / query the current database container CON_NAME--ORCLPDBSQL > create user lzj identified by 123456; / / create a user in PDB (no need to add caching #) the user has been created. SQL > alter user lzj identified by 654321; / / modify user password: user has changed. SQL > grant connect to lzj; / / the authorization to the user was successful. SQL > alter session set container=cdb$root; / / switch to CDB container session has changed. SQL > show con_name; / / View the current container CON_NAME--CDB$ Root 5, import test data

In previous versions of Oracle 12c, scott users were defaulted after installation, and tables for testing were stored in this user mode, while there were no scott users by default after Oracle 12c installation. For future testing convenience, here is how to import test data in Oracle 12c.

Download the test.sql script and do the following:

[oracle@oracle] $ll / / prepare the script test file total amount of 8 oracle oinstall RW Rafael-1 oracle oinstall 7658 June 15 2017 test.sql [oracle@oracle] $sqlplus / as sysdba SQL*Plus: Release 12.2.0.1.0 Production on Saturday November 30 17:19:15 2019Copyright (c) 1982, 2016, Oracle. All rights reserved. Connect to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0-64bit ProductionSQL > create user c##scott identified by scott default tablespace users temporary tablespace temp quota unlimited on users;// create user c##scott user has been created. SQL > grant connect,resource to cantilever score; / / user authorization succeeded. SQL > @ test.sql / / Import the script file without a path to indicate the current directory. / / the creation process omits SQL > conn cantilever scottpoint; / / switch that the user c##scott is connected. SQL > show user; / / check that the current user USER is "C##SCOTT" SQL > col tname for A10; / / format the output so that all columns are displayed in a row, and adjust the width of the tname column to 10SQL > select * from tab / / query all tables under the current user TNAME TABTYPE CLUSTERID- BONUS TABLEDEPT TABLEEMP TABLESALGRADE TABLESQL > desc emp / / whether the structure name of the query emp table is empty? Type-EMPNO NOT NULL NUMBER (4) ENAME VARCHAR2 (10) JOB VARCHAR2 (9) MGR NUMBER (4) HIREDATE DATE SAL NUMBER (7) COMM NUMBER (7) DEPTNO NUMBER (2) SQL > col empno for 9999 / / formatted output. Empno is listed as a number, and 9999 represents a width of 4 SQL > select * from emp. / / modify it according to the actual situation How do you look? EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO--7369 SMITH CLERK 7902 17-December-80800 20 7499 ALLEN SALES 7698 20-February-81 1600 1600 30 MAN 7521 WARD SALES 7698 22-February-81 1250 1250 30 MAN 7566 JONES MANAG 7839 02-April-81 2975 20 ER 7654 MARTI SALES 7698 28-September-81 1250 1400 30EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO--N MAN 7698 BLAKE MANAG 7839 01-May-81 2850 30 ER 7782 CLARK MANAG 7839 09-June-81 2450 10 ER 7788 SCOTT ANALY 7566 19-April-87 3000 20 STEMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO- -7839 KING PRESI 17-November-81 5000 10 DENT 7844 TURNE SALES 7698 08-September-81 1500 030 R MAN 7876 ADAMS CLERK 7788 23-May -87 1100 20 7900 JAMES CLERK 7698 03-December-81 950 30 7902 FORD ANALY 7566 03-December-81 3000 20 STEMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO- -7934 MILLE CLERK 7782 23-January-82 1300 10 R 14 rows selected. SQL > select * from cantilever score. Emp. if you are using a non-c##scott user, you need to specify a user. Table name

-this is the end of this article. Thank you for reading-

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