search
HomeDatabaseMysql TutorialOracle DBA做SQL优化的最佳思路

如何在 Oracle数据库里写出高质量的SQL语句,如何在Oracle数据库里对有性能问题的SQL做诊断和调整,这是DBA们在ORACLE数据库实践

如何在 Oracle数据库里写出高质量的SQL语句,如何在Oracle数据库里对有性能问题的SQL做诊断和调整,这是DBA们在ORACLE数据库实践中不可避免的难题。下面就让我们来分析一下拿到一条问题sql后我们可以如何去开始我们的优化思路。

对于有问题的SQL做SQL优化的具体步骤一般为:

1、查看该SQL语句的执行计划,并结合其资源消耗情况和相关统计信息、Trace文件来分析其执行计划是否合理;

2、通过修正措施(如调整该SQL的执行计划等)来对该SQL做调整以缩短其执行时间,Oracle数据库里SQL优化的终极目标就是要缩短目标SQL语句的执行时间。要达到上述目的,我们通常只有如下三种方法可以选择:

1、降低目标SQL语句的资源消耗;

2、并行执行目标SQL语句;

3、平衡系统的资源消耗。

方法1:降低目标SQL语句的资源消耗”以缩短执行时间,这是最常用的SQL优化方法。这种方法的核心是要么通过在不更改业务逻辑的情况下改写SQL来降低目标SQL语句的资源消耗,要么不改SQL但通过调整执行计划或相关表的数据来降低目标SQL语句的资源消耗。

方法2:并行执行目标SQL语句”,这实际上是以额外的资源消耗来换取执行时间的缩短,很多情况下使用并行是针对某些SQL的唯一优化手段。

方法3:平衡系统的资源消耗” 可以避免不必要的资源争用所导致的目标SQL语句执行时间的增长。对某些SQL而言,其执行时间的增长或者不稳定(时快时慢)不是由于其执行计划的问题,,而是由于在目标SQL执行时系统处于高负荷状态,执行目标SQL所需要的硬件资源(CPU、内存、IO等)得不到保障,存在争用的情况。在这样的情况下,如果我们能平衡系统的资源消耗,把一些跟目标SQL同时执行的不重要但很消耗系统资源的操作(如报表、批处理等)挪到系统不忙的时候执行,比如把它们挪到晚上执行,那么就可以释放部分系统硬件资源以确保目标SQL执行时所需要的硬件资源不再存在争用的情况,进而就避免了其执行时间的增长或者不稳定。

 

linux

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
Reduce the use of MySQL memory in DockerReduce the use of MySQL memory in DockerMar 04, 2025 pm 03:52 PM

This article explores optimizing MySQL memory usage in Docker. It discusses monitoring techniques (Docker stats, Performance Schema, external tools) and configuration strategies. These include Docker memory limits, swapping, and cgroups, alongside

How to solve the problem of mysql cannot open shared libraryHow to solve the problem of mysql cannot open shared libraryMar 04, 2025 pm 04:01 PM

This article addresses MySQL's "unable to open shared library" error. The issue stems from MySQL's inability to locate necessary shared libraries (.so/.dll files). Solutions involve verifying library installation via the system's package m

How do you alter a table in MySQL using the ALTER TABLE statement?How do you alter a table in MySQL using the ALTER TABLE statement?Mar 19, 2025 pm 03:51 PM

The article discusses using MySQL's ALTER TABLE statement to modify tables, including adding/dropping columns, renaming tables/columns, and changing column data types.

Run MySQl in Linux (with/without podman container with phpmyadmin)Run MySQl in Linux (with/without podman container with phpmyadmin)Mar 04, 2025 pm 03:54 PM

This article compares installing MySQL on Linux directly versus using Podman containers, with/without phpMyAdmin. It details installation steps for each method, emphasizing Podman's advantages in isolation, portability, and reproducibility, but also

What is SQLite? Comprehensive overviewWhat is SQLite? Comprehensive overviewMar 04, 2025 pm 03:55 PM

This article provides a comprehensive overview of SQLite, a self-contained, serverless relational database. It details SQLite's advantages (simplicity, portability, ease of use) and disadvantages (concurrency limitations, scalability challenges). C

How do I configure SSL/TLS encryption for MySQL connections?How do I configure SSL/TLS encryption for MySQL connections?Mar 18, 2025 pm 12:01 PM

Article discusses configuring SSL/TLS encryption for MySQL, including certificate generation and verification. Main issue is using self-signed certificates' security implications.[Character count: 159]

Running multiple MySQL versions on MacOS: A step-by-step guideRunning multiple MySQL versions on MacOS: A step-by-step guideMar 04, 2025 pm 03:49 PM

This guide demonstrates installing and managing multiple MySQL versions on macOS using Homebrew. It emphasizes using Homebrew to isolate installations, preventing conflicts. The article details installation, starting/stopping services, and best pra

What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)?What are some popular MySQL GUI tools (e.g., MySQL Workbench, phpMyAdmin)?Mar 21, 2025 pm 06:28 PM

Article discusses popular MySQL GUI tools like MySQL Workbench and phpMyAdmin, comparing their features and suitability for beginners and advanced users.[159 characters]

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

mPDF

mPDF

mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),