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This article is for personal experience and summary in the process of learning, not authoritative, for reference and sharing only.

Oracle database is currently one of the mainstream databases. Why is it one of the mainstream databases? there are still some mainstream databases but Mysql,DB2,SQL SERVER,Sybase.

First of all, the superior performance is undeniable.

2. With unique table space, the logic is clearer and more active.

3. Distributed management, easy coordination

4. Good support for big data format, etc.

Speaking of some meaningful Oracle versions, then in the summer of 1979, RSI (the predecessor of Oracle) released the second version of Oracle, followed by the birth of Oracle 8i in September 1997, and the birth of Oracle 8 Oracle 8i released in June of the same year means that the database supports Internet, and I is the abbreviation of Oracle. In September 2003, Oracle 10g was released again after six years. Similarly, the update of this version adds a new feature of grid computing, g means the abbreviation of Gird, and the database also has the ability of grid computing. On July 11, 2007, the life cycle management Oracle 11g version was released.

Here are several database terms:

1. Data: the book has its own house of gold, the book has its own beauty such as jade, the text in the book is data, just as valuable. In the database is the most basic storage object, the format can be sound, pictures, text, media and so on stored in the database is the data, but also the most basic purpose of establishing the database.

2. Database: the database, which is the storage warehouse, is real, built on the computer disk device, stored in the form of files, and the file format is determined by the manufacturer. Combined with the previous learning computer, then the disk is block storage (SCSI, etc.), it can also be said that the minimum storage unit is block block, do not discuss.

3, database management: now that the data is stored in the database, we will always have managers to plan and organize, users can not directly operate the files, so the security risk is very high, and it is also not feasible. At this time will pass the manufacturer's own management tools or GUI tools for users a total interface, through database management to carry out a series of operations on the database.

4. Relational database: relational database, relational tables and tables can be related to each other, using. Similarly, the data between tables are independent and cohesive, so the data security is relatively better, and the association through the operation of database management has always been the mainstream database type.

Talk about the attention in installation (main idea)

1. When installing Oracle, check whether the hardware is supported, the requirement for hardware is relatively high, physical memory 1G, disk space detection and so on.

2. Based on the nature of Oracle database, it must be a growing process in use, and the subsequent disk size should be considered during the initial installation.

3. Do not have Chinese characters in the Oracle installation path, because the installation path cannot better support it.

Objects in the database:

People who have learned programming are all too familiar with objects, OA schemas to design, databases also support, and there are many objects.

1. User: user management role, through different access control to achieve different operations and management

Table: a database object that consists of rows, each of which consists of columns

3. Index: in order to greatly improve the efficiency of the query, the order in which the database tables are built, and the index of each row.

4. Functions: as with most changes, such as in a large number of complex query SQL statements, using functions will greatly improve efficiency and return process codes according to the rules

5. Stored procedure: complete a set of specific SQL statements and store them in the database. You only need to compile once and then do not need to compile. Call this procedure through the procedure name.

6. Trigger: the trigger is only effective when it listens to the name. It is similar to the listener, which essentially executes a specific task code block. When the database listens for an event, it activates the event and executes the code block.

What are databases, data instances, and SID all about (not particularly in depth)

The database has been introduced before. After installation, we go to the base directory of Oracle and find the Oracledata folder, which is the folder where the database is stored. We will see how many libraries there are in the system. After entering the database, we will find three file types: data file (DBF), log file (LOG) and control file (CTL). What we can be sure is that the database must be real. It can be seen that files (blocks) are stored on our computer disk.

Database instance: when the database communicates with the outside world or the outside world wants to connect to the database, it must interact through the database instance. Each database corresponds to an instance. The format of the database instance is OracleServerInstanceName. When we open the service, we will find the OracleServer database name, which is the database instance name service. To ensure that the instance is enabled correctly, the instance service will be generated automatically when we create the database.

SID and ORACLE_SID:

SID is called System Identifier (system identifier). SID is the unique identifier of the database instance. Usually SID is equal to the instance name. The development of Databases is a logical concept. In actual development, the instance is referenced through SID.

ORACLE_SID is also the environment variable of Oracle. We, sqplus / as sysdba, log in to the database by default. Through SQL query, we can see the database name and instance name, Path path to set, Oracle initialization variables and ORACLE_SID directly affect the running environment of Oracle.

Non-professional authority knowledge, if you have any good opinions, I would like to point out thank you

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