MySQL是一种常见的关系型数据库管理系统，它是开源的，可用于在各种平台上创建数据库。MySQL 5.5版本的发布带来了很多性能和扩展方面的改进，特别是在存储引擎方面的改进。在本文中，我们将介绍如何在CentOS 7上安装MySQL 5.5。

步骤1：安装MySQL Yum Repository

MySQL Yum Repository提供了许多MySQL版本和操作系统版本的安装包。我们需要把MySQL Yum Repository添加到我们的系统中。您可以在 https://dev.mysql.com/downloads/repo/yum/ 上找到最新版本。

使用以下命令在CentOS上安装MySQL Yum Repository。

$ sudo yum install wget

$ sudo wget https://dev.mysql.com/get/mysql57-community-release-el7-11.noarch.rpm

$ sudo rpm -ivh mysql57-community-release-el7-11.noarch.rpm

步骤2：安装MySQL 5.5

在安装MySQL 5.5之前，请确保您的系统安装了yum-utils。

$ sudo yum install yum-utils

使用以下命令列出可用版本。

$ sudo yum list mysql-community-server --showduplicates | sort -r

您应该看到类似以下的输出。

mysql-community-server.x86_64 5.7.24-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.23-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.22-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.21-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.20-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.19-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.18-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.17-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.16-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.15-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.14-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.13-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.12-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.11-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.10-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.9-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.8-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.7-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.6-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.5-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.4-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.3-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.2-1.el7 mysql57-community

mysql-community-server.x86_64 5.7.1-1.el7 mysql57-community

mysql-community-server.x86_64 5.6.41-2.el7 mysql56-community

mysql-community-server.x86_64 5.6.40-2.el7 mysql56-community

mysql-community-server.x86_64 5.6.39-2.el7 mysql56-community

mysql-community-server.x86_64 5.6.38-1.el7 mysql56-community

mysql-community-server.x86_64 5.6.37-1.el7 mysql56-community

mysql-community-server.x86_64 5.6.36-1.el7 mysql56-community

mysql-community