【单选题】下面正确表示Employees表中有多少非NULL的Region列的SQL语句是()
A. SELECT count(* ) from Employees B. SELECT count(Region) from Employees C. SELECT count(Distinct Region) from Employees D. SELECT sum(ALL Region) from Employees
A. SELECT count(* ) from Employees B. SELECT count(Region) from Employees C. SELECT count(Distinct Region) from Employees D. SELECT sum(ALL Region) from Employees
举一反三
- 表employees中有字段title表示职务，字段salary表示工资，求各个职务平均工资的T-SQL语句是（ ）。 A: SELECT AVG(SALARY) FROM EMPLOYEES WHERE TITLE B: SELECT AVG(SALARY) FROM EMPLOYEES GROUP BY TITLE C: SELECT AVG(TITLE) FROM EMPLOYEES GROUP BY SALARY D: SELECT SALARY FROM EMPLOYEES GROUP BY TITLE
- Employees表中lastname列保存顾客的姓，firstname列保存顾客的名。现在需要查询顾客姓名的组合，例如lastname列中的“张”，同一行firstname列中的“国华”，查询结果应该返回“张国华”，则正确的查询语句应该是（） A: select lastname,firstname from employees B: select * from employees order by lastname,firstname C: select lastname+firstname from employees D: select lastname and firstname from employees
- 若需统计“选课”表中已经选修了课程的学生人数，下面语句正确的是( )。 A: SELECT COUNT(DISTINCT学生号)FROM选课 B: SELECT COUNT(学生号)FROM选课 C: SELECT COUNT(*)FROM选课 D: SELECT COUNT(DISTINCT*)FROM选课
- 以下SQL语句中，____________可以在“学生-课程”数据库正确实现“查询选修了课程的学生总人数”。 A: SELECT COUNT(Sno)FROM SC B: SELECT COUNT(DISTINCT Sno)FROM SC C: SELECT COUNT(*)FROM SC D: SELECT SUM(Sno)FROM SC
- 以下哪条语句可以实现查询选了课的学生人数（ ）。 A: select count(*) from sc B: select count(sno) from sc C: select count(distinct sno) from sc D: select count(cno) from sc