ORACLE DATABASE

关系数据库的数据结构是指一些相关的表和其他数据库对象的集合。对于关系数据库来说，关系就是表的同义词。表由行和列组成（类似二维数组的结构）。列包含一组命名的属性（也称字段），行包含一组记录，每行对应一条记录。行和列的交集称为数据项，指出了某列对应的属性在某行上的值，也称为字段值。列需定义数据类型，比如整数或者字符型的数据。

Oracle Database的秘密,经典系列

Oracle数据库函数是数据库管理系统Oracle中实现特定计算或数据处理的核心工具。它们分为多种类型，包括聚合函数、分析函数、转换函数、数学函数等，广泛应用于数据查询、数据分析和报表生成等场景。 一、聚合函数是Oracle中最常见的函数之一，它们用于对一组值进行汇总，返回单个结果。例如：1. SUM()：计算指定列的所有值的总和。2. COUNT()：计算非空值的数量，可选择性地指定列名以计算特定列的非空值数量。3. AVG()：计算平均值。4. MAX()和MIN()：找出指定列的最大值和最小值。 二、分析函数是Oracle 8.1.6引入的新特性，与聚合函数不同的是，它们在每个分组内返回多行，而不是单一的聚合值。分析函数主要用于复杂的数据分析和统计。基本语法如下： (,...) OVER ( ) ：如RANK(), ROW_NUMBER(), LAG(), LEAD(), AVG()等，它们可以接受0-3个参数。 OVER：关键字标识这是一个分析函数。 PARTITION BY：将数据逻辑上划分为多个分区，每个分区独立进行分析。 ORDER BY：定义在每个分区内的行排序方式，包括升序(ASC)、降序(DESC)以及空值处理(NULLS FIRST/NULLS LAST)。 WINDOWING CLAUSE：定义一个固定或动态的数据窗口，分析函数将在这个窗口内计算值。 常见的分析函数包括：- RANK()：为每个分区内的行分配唯一的排名。- ROW_NUMBER()：为每个分区内的行分配唯一的行号。- LAG()和LEAD()：获取当前行之前或之后的行的值。- PERCENT_RANK()：计算每个行在分区中的百分比排名。- NTILE()：将分区内的行分成n个桶，并为每个桶分配一个编号。 三、ROLLUP和CUBE是GROUP BY语句的扩展，提供了多级分组的功能：1. ROLLUP：生成所有可能的子集组合，从最细粒度的分组到最粗粒度的全表分组。例如，GROUP BY ROLLUP(A, B, C)会生成(A,B,C), (A,B), (A),和()的结果。2. CUBE：生成所有可能的分组组合，包括单列、两列、三列直至所有列的组合。

Oracle is one of the most widely used database management systems, offering a rich set of features and powerful performance. This Oracle Study Note covers the basics of database management and SQL, providing an in-depth exploration of key concepts. Data Dictionary: Oracle's data dictionary consists of a series of views and tables that store information about database objects, privileges, and other metadata. For example, dba_tablespaces provides the status of all tablespaces, dba_users displays user information, user_sys_privs lists system privileges for users, and user_tab_privs_made records table permissions granted to other users. Other views, such as user_col_privs_made and user_role_privs, help monitor and manage column-level and role-based permissions. SQL Statements: SQL is the language used to interact with Oracle. It includes commands for creating users, modifying user properties (such as passwords and default tablespaces), granting and revoking privileges, creating and managing objects (like tables, columns, and constraints), and performing data operations (insert, update, delete). For instance, CREATE USER creates a new user, ALTER USER modifies user attributes, GRANT and REVOKE manage privileges, and INSERT INTO, UPDATE, and DELETE FROM are used to manipulate data. Constraints and Indexes: Oracle offers various types of constraints, such as NOT NULL, PRIMARY KEY, UNIQUE, FOREIGN KEY, and CHECK, which ensure data integrity and consistency. Indexes speed up data retrieval. Views and Synonyms: A view is a virtual table based on one or more tables, simplifying complex queries and protecting data. A synonym provides an alias for objects, allowing users to access different objects with the same name, improving database accessibility. Transactions and Rollbacks: In Oracle, a transaction is a group of logical operations that must either all succeed or all fail, ensuring data consistency. Use COMMIT to commit a transaction, ROLLBACK to undo changes, and SAVEPOINT to set a rollback point. SQL Utility Commands: Useful SQL commands include DESCRIBE (to view table structure), SELECT * FROM dual (for connection testing), SPOOL (to save query results to a file), SHOW (to display session settings), and HELP (to provide help information).

The Oracle Architecture is composed of several layers that work together to provide a robust, scalable database system. At the core is the Oracle Database, which relies on a multi-tiered architecture for storage and management of data. Key components include the Instance, which is made up of memory structures like the System Global Area (SGA) and background processes like the Database Writer. The Database Storage layer handles physical data files, and the User Layer interacts with the system through SQL queries and applications. The architecture is designed to optimize performance, scalability, and security, ensuring data integrity and high availability.

The Oracle Database Administrator Guide covers a wide range of topics essential for managing Oracle databases. It includes Oracle basics such as tables, views, indexes, and PL/SQL. Installation and configuration on various operating systems, database creation, and service setup are explored in detail. Key topics like data storage structures, user management, and security ensure administrators can properly manage permissions and prevent unauthorized access. Backup and recovery strategies, performance monitoring, optimization techniques, troubleshooting, high availability, disaster recovery, and database migration are all included for a complete skill set. PL/SQL programming is also part of the curriculum for advanced database handling.

Oracle Database在线文档以CHM格式提供，双击index.chm即可开启文档。多个CHM文档相互独立，支持跨文档索引和搜索，方便使用，这是其优于PDF格式的优势之一。

数据库的启动步骤： 启动 Server Manager 连接 INTERNAL 用户 启动实例 读取 参数文件 分配 SGA 启动 后台进程 打开 后台跟踪文件

为了创建安装Oracle数据库，必须满足下面的条件:1. 操作系统权限2. 数据库权限3. 足够的磁盘空间4. 足够的内存空间

Oracle数据库在Linux上的安装步骤 准备环境：确保Linux系统符合Oracle数据库的安装要求。安装必要的依赖包，如yum install -y oracle-database-preinstall-19c。 下载Oracle数据库安装包：从Oracle官网或其官方镜像站下载Oracle 19c的安装包。 创建用户和组：执行以下命令创建oracle用户和dba组：bashgroupadd dbauseradd -g dba oracle 配置内核参数和限制：编辑/etc/sysctl.conf文件，添加以下内核参数：bashfs.file-max = 6815744kernel.shmmax = 4294967296kernel.shmall = 2097152执行sysctl -p应用更改。 解压安装包：将下载的Oracle安装包解压到指定目录。 安装Oracle数据库：进入解压后的目录，运行以下命令启动安装：bash./runInstaller 运行配置脚本：安装完成后，执行以下命令配置数据库：bash/etc/init.d/oracledb_ORCLCDB configure 验证安装：使用sqlplus命令验证Oracle数据库是否安装成功。 完成安装：设置Oracle数据库服务开机自启动并确保数据库正常运行。 通过以上步骤，您可以在Linux系统上顺利安装Oracle数据库并进行初步配置。