查询scott用户的emp表中的总记录数,可以使用下列哪个语句?() A: SELECT MAX(empno) FROM scott.emp; B: SELECT<br/>COUNT(empno) FROM scott.emp; C: SELECT COUNT(comm) FROM scott.emp; D: SELECT COUNT(*) FROM scott.emp;

employee表中lastname列保存顾客姓，firstname列保存顾客的名，现在，需要查询顾客的姓名的组合，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 employee B: select * from employee order by lastname,firstname C: select lastname+firstname from employee D: select lastname and firstname from employee

执行语句“SELECT COUNT (*) FROM human”将返回（ ）行

【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

补全语句：select vend_id,count(*) from products where prod_price>=10 group by vend_id ____ count(*)>=2;