在oracle中,用户权限分为:系统权限和对象权限,系统权限:指在数据库级别执行某种操作的权限,如,create session权限,create
权限管理
权限管理概述
在Oracle中,用户权限分为:系统权限和对象权限
系统权限:指在数据库级别执行某种操作的权限,如,create session权限,create any table权限
对象权限:指对某个特定的数据库对象执行某种操作的权限,如对表的增删改查的权限
将权限授予用户的两种方法:
(1)直接授权:利用grant命令直接为用户授权
(2)间接授权:先将权限授予角色,然后再将角色授予用户
DBA 的权限控制包括:
• 为用户提供执行某种操作的权限
• 授予和撤消执行系统功能的权限
• 将权限直接授予用户或角色
• 将权限授予所有用户(PUBLIC)
一,系统权限管理
1.系统权限分类
在oracle数据库中,有一百多中系统权限。可以讲系统权限授予用户,角色,public用户组、
注意:public用户组时创建数据库的时候自动创建的一个用户组,数据库中所有用户都属于该用户组;如果将某个权限授予public用户组,,则数据库中所有过的用户都具备该权限
常用的系统权限有:
CREATE SESSION 创建会话
CREATE SEQUENCE 创建序列
CREATE SYNONYM 创建同名对象
CREATE TABLE 在用户模式中创建表
CREATE ANY TABLE 在任何模式中创建表
DROP TABLE 在用户模式中删除表
DROP ANY TABLE 在任何模式中删除表
CREATE PROCEDURE 创建存储过程
EXECUTE ANY PROCEDURE 执行任何模式的存储过程
CREATE USER 创建用户
DROP USER 删除用户
CREATE VIEW 创建视图

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

MySQL is an open source relational database management system suitable for data storage, management, query and security. 1. It supports a variety of operating systems and is widely used in Web applications and other fields. 2. Through the client-server architecture and different storage engines, MySQL processes data efficiently. 3. Basic usage includes creating databases and tables, inserting, querying and updating data. 4. Advanced usage involves complex queries and stored procedures. 5. Common errors can be debugged through the EXPLAIN statement. 6. Performance optimization includes the rational use of indexes and optimized query statements.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

InnoDB's lock mechanisms include shared locks, exclusive locks, intention locks, record locks, gap locks and next key locks. 1. Shared lock allows transactions to read data without preventing other transactions from reading. 2. Exclusive lock prevents other transactions from reading and modifying data. 3. Intention lock optimizes lock efficiency. 4. Record lock lock index record. 5. Gap lock locks index recording gap. 6. The next key lock is a combination of record lock and gap lock to ensure data consistency.

The main reasons for poor MySQL query performance include not using indexes, wrong execution plan selection by the query optimizer, unreasonable table design, excessive data volume and lock competition. 1. No index causes slow querying, and adding indexes can significantly improve performance. 2. Use the EXPLAIN command to analyze the query plan and find out the optimizer error. 3. Reconstructing the table structure and optimizing JOIN conditions can improve table design problems. 4. When the data volume is large, partitioning and table division strategies are adopted. 5. In a high concurrency environment, optimizing transactions and locking strategies can reduce lock competition.

In database optimization, indexing strategies should be selected according to query requirements: 1. When the query involves multiple columns and the order of conditions is fixed, use composite indexes; 2. When the query involves multiple columns but the order of conditions is not fixed, use multiple single-column indexes. Composite indexes are suitable for optimizing multi-column queries, while single-column indexes are suitable for single-column queries.

To optimize MySQL slow query, slowquerylog and performance_schema need to be used: 1. Enable slowquerylog and set thresholds to record slow query; 2. Use performance_schema to analyze query execution details, find out performance bottlenecks and optimize.

MySQL and SQL are essential skills for developers. 1.MySQL is an open source relational database management system, and SQL is the standard language used to manage and operate databases. 2.MySQL supports multiple storage engines through efficient data storage and retrieval functions, and SQL completes complex data operations through simple statements. 3. Examples of usage include basic queries and advanced queries, such as filtering and sorting by condition. 4. Common errors include syntax errors and performance issues, which can be optimized by checking SQL statements and using EXPLAIN commands. 5. Performance optimization techniques include using indexes, avoiding full table scanning, optimizing JOIN operations and improving code readability.


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