21、您有一个Employee的表，包括以下列：lEmployeeIDlEmployeeName您应该使用那种语句以返回表的行数？
A: SELECT COUNT(rows) FROM Employee
B: SELECT COUNT(*) FROM Employee
C: SELECT * FROM Employee
D: SELECT SUM(*) FROM Employe
A: SELECT COUNT(rows) FROM Employee
B: SELECT COUNT(*) FROM Employee
C: SELECT * FROM Employee
D: SELECT SUM(*) FROM Employe
举一反三
- Select count(*) from employee 语句得到的结果是（）。
- 在员工管理系统中，查询表employee表中所有员工的姓名，字段:id(int),firstname(varchar),lastname(varchar),以下sql语句正确的是（）。 A: Select firstname +’.’+ lastname as ‘name’ from employee B: Select firstname +’.’+ lastname from employee C: Select ‘name’= firstname +’.’+ lastname from employee D: Select firstname,lastname from employee
- 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
- 通过 SQL，您如何返回 "Persons" 表中记录的数目？ A: SELECT COLUMNS() FROM Persons B: SELECT COLUMNS(*) FROM Persons C: SELECT COUNT() FROM Persons D: SELECT COUNT(*) FROM Persons
- 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;