下列（）是SQL语言查询出员工E_mail地址的语句。
- A、select staffno from staff where E_mail＝NULL
- B、select staffno from staff where E_mail NULL
- C、select staffno from staff where E_mail is NULL
- D、select staffno from staff where E_mail is not NULL
正确答案:D
答案解析:有
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中学教师资格证信息技术(统考)