查询数据是数据库系统应用的主要内容，用数据库保存数据就是为了使用，要使用就要首先查找到需要的数据。数据库查询主要是根据用户提供的限定条件，从可用的数据库表返回符合限定条件的数据库记录，执行查询的语句是SELECT语句。
在讲述SELECT语句之前，需要运行Navicat查询器，在mooc数据库course表插入相关记录。启动Navicat连接mooc数据库，【单击】工具条的查询按钮，在工具条下方的导航条中选择【新建查询】，进入查询窗口，输入下面的查询语句。
insert into course (number,price,brief,category,teacher_number,name) value("0001",43,"详细讲述Java编程","编程","0001","快速掌握Java");
insert into course (number,price,brief,category,teacher_number,name) value("0002",29,"详细讲述数据库编程","数据库","0002","MySQL数据库技术应用");
insert into course (number,price,brief,category,teacher_number,name) value("0003",39.2,"详细讲述Python编程","编程","0001","快速掌握Python");
insert into course (number,price,brief,category,teacher_number,name) value("0004",45,"详细讲述SQL Server应用","数据库","0002","SQL Server数据库");
insert into course (number,price,brief,category,teacher_number,name) value("0005",39,"详细讲述语音识别技术","机器学习","0003","语音识别技术");
insert into course (number,price,brief,category,teacher_number,name) value("0006",56,"详细讲述自然语言处理技术","机器学习","0003","自然语言处理");下图是执行效果。
