[单项选择]According to the professor, which of the following activities is not included in marketing A. Analyzing customers needs. B. Securing necessary information. C. Designing and producing goods or services. D. Creating and maintaining relationships.
第21题: [单项选择]在SQL语言的SELECT语句中,实现投影操作的是哪个子句 ( ) A. SELECT B. FROM C. WEHERE D. GROUP BY 参考答案:A 答案解析:[解析] 本题考查SQL语言的功能。 FROM是指定操作关系,WHERE是指定操作条件, GROUP BY是指定分组条件,SELECT是指定查询后显示的字段即投影。故本题选择A。