Oracle Database Learning Introduction, basic understanding

Based on the relational database SQL Server has been contacted, the database, tables, records, table additions and deletions to the operation of these basic concepts have been understood.
Oracle is an object-based relational database, and Oracle also stores and manages data in the form of tables, and Oracle adds some object-oriented ideas.

Oracle database is the core product of Oracle (Chinese name Oracle) and Oracle database is a
Database management system for large and medium-sized enterprises. In all database management systems (e.g. Microsoft SQL Server,
IBM's DB2, etc.), Oracle's main users are very broad, including: banking, telecommunications, mobile communications, aviation,
Insurance, Finance, e-commerce and transnational corporations. Oracle products are free of charge and can be downloaded from Oracle's official website
To the installation package, on the other hand Oracle services are charged.
Since the founding of Oracle, from the initial database version to Oracle7, Oracle8i, oracle9i,oracle10g
To oracle11g, although there is a certain difference in operation between each version, Oracle's operational base of data
The SQL standard is followed in this. Therefore, there is little difference between versions for Oracle development.

Oracle Home directory location is the location where Oracle is ready to install, called "Oracle_home", the general Oracle root
The current computer's hard disk size is given a suitable location by default. Oracle software can be installed at
You can then create the database separately, or in the Select the Create Startup database check box to install the Oracle production
When creating a database, it is recommended for beginners to install it. Fill in the global database name, and manage
Member's password. The global database name is the unique identity of the database in the server network.

The database is created with a series of memory spaces and background processes that provide services to the database, called the database's
Instance. Each database will have at least one instance for its service. The memory structure in the instance is called the system Global Area (SGA),
The system allocates very considerable memory space for the SGA based on the performance of the current computer system.

Oracle creation database cannot be done with a simple CREATE DATABASE command like SQL Server,
You also need to configure various parameters during the database creation process. Although there are DBCA tool wizards, it is still necessary to
More cumbersome configuration.

Although multiple databases can be installed in an Oracle database server, a database needs to occupy a non-
Large memory space, so a server typically installs only one database. Each database can have a very
Multiple users, different users have their own database objects (such as: Database tables), a user if access
The other user's database object must be granted certain permissions by the other user. A table created by a different user,
can only be accessed by the current user. So in Oracle development, different applications need to use different users
Access.

Once the Oracle server is successfully installed, the Oracle server can be connected via the client tool to Oracle
Official download Oracle-specific client software, most of the client tools are based on Oracle client software. Pick up the
To introduce several common Oracle client tools.
? Sql*plus Tools
This tool is a client tool that comes with the default installation of the Oracle system. On the Windows command line, enter
"SQLPLUSW" command, you can start the tool.

After entering the user name and password, if the sql*plus is on the same computer as the database server and the current service is
There is only one DB instance under the server, the "host string" may not be filled

Sql*plus command-line tools
This command-line tool provides the ability to interact with the database and the ability to maintain the database, including Oracle's own
The full functionality of the Sql*plus tool is often used in Oracle management. On the command line, enter: "Sqlplus/nolog"
To start the tool.

In an Oracle database, by default, all system data, SQL keywords, and so on are capitalized, in the operation
Process, Oracle automatically converts the content to uppercase, so the user does not need to consider the case when working.
In general, in order to good program style, the program is recommended to use uppercase keywords, non-keywords can be used
Lowercase.

Oracle Database Learning Introduction, basic understanding