获取执行计划EXPLAN PLAN-Mysql Tutorial-php.cn

Home

Database

Mysql Tutorial

获取执行计划EXPLAN PLAN

WBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWBOYWB

Jun 07, 2016 pm 03:22 PM

generallyimplementObtainplan

一般获取执行计划有四种途径：1、执行explain plan，查询结果输出表。2、查询动态性能视图，它显示缓存在库缓存中的执行计划（有时查不出结果是因为执行计划已经不在库缓存中）。3、查询AWR或Statspack表。4、启动提供执行计划的跟踪功能（set autotrace tra

一般获取执行计划有四种途径：1、执行explain plan，查询结果输出表。2、查询动态性能视图，它显示缓存在库缓存中的执行计划（有时查不出结果是因为执行计划已经不在库缓存中）。3、查询AWR或Statspack表。4、启动提供执行计划的跟踪功能（set autotrace trace explain）。使用得比较多的是第四种，简单又好用~本篇讲第一种方法。

首先，explainplan原理就是把一条SQL语句分析一下，将该语句的执行计划和相关信息存储到计划表（plan table）中。可以查看一下联机文档关于explain plan的语法，

这里的string是用于区分计划表中多个执行计划的，into后面的table就是“计划表”。一般的使用方法是explain plan for “sql text”;之后select * fromtable(dbms_xplan.display);有时出现这种情况，explain plan for insert into test select * from test; 此时任何事务并无变化，因为explainplan是DML语句，不会对当前事务隐式提交，仅仅是插入几条记录到计划表。

我们会把执行计划与相关信息存入计划表，默认计划表是sys下的一张表，但有一个plan_table公共同义词，当你想使用一个私有的计划表时，可以运行utlxplan.sql脚本。

当分析的sql语句有绑定变量时，一般使用绑定变量进行explain for，而不是使用几个常量代入绑定变量进行分析。在explain for使用绑定变量也有两个问题。第一，默认情况下绑定变量是varchar2类型，所以在执行计划access中会有一个显式类型转换；第二，不能使用bind peeking。

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Explain the InnoDB Buffer Pool and its importance for performance.Apr 19, 2025 am 12:24 AM

InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

MySQL vs. Other Programming Languages: A ComparisonApr 19, 2025 am 12:22 AM

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages have advantages in their respective fields such as data analytics, enterprise applications, and system programming.

Learning MySQL: A Step-by-Step Guide for New UsersApr 19, 2025 am 12:19 AM

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.

MySQL: Essential Skills for Beginners to MasterApr 18, 2025 am 12:24 AM

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL: Structured Data and Relational DatabasesApr 18, 2025 am 12:22 AM

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL: Key Features and Capabilities ExplainedApr 18, 2025 am 12:17 AM

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

The Purpose of SQL: Interacting with MySQL DatabasesApr 18, 2025 am 12:12 AM

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

MySQL for Beginners: Getting Started with Database ManagementApr 18, 2025 am 12:10 AM

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA

See all articles