SQL语句的执行效率问题试题及答案.docx

SQL语句的执行效率问题试题及答案

姓名：____________________

一、单项选择题（每题2分，共10题）

1.以下哪个SQL语句中存在执行效率问题？

A.SELECT*FROMStudentsWHEREAge20;

B.SELECTName,AgeFROMStudentsWHEREAge20;

C.SELECT*FROMStudentsWHEREName=张三;

D.SELECTName,AgeFROMStudentsWHEREName=张三;

2.在以下SQL语句中，使用索引可以显著提高查询效率的是：

A.SELECT*FROMEmployeesORDERBYSalary;

B.SELECT*FROMEmployeesWHEREDepartmentID=10;

C.SELECT*FROMEmployeesWHEREAgeBETWEEN20AND30;

D.SELECT*FROMEmployeesWHERENameLIKE%李%;

3.以下哪个SQL语句会导致全表扫描？

A.SELECT*FROMOrdersWHEREOrderDate=2025-01-01;

B.SELECT*FROMOrdersWHERECustomerID=1;

C.SELECT*FROMOrdersWHEREOrderID=100;

D.SELECT*FROMOrdersWHEREStatus=Shipped;

4.以下哪个SQL语句可以有效地利用索引？

A.SELECT*FROMProductsWHEREPrice100;

B.SELECT*FROMProductsWHERECategory=Electronics;

C.SELECT*FROMProductsWHERECategory=ElectronicsANDPrice100;

D.SELECT*FROMProductsWHERECategory=ElectronicsANDPriceBETWEEN100AND200;

5.以下哪个SQL语句可以减少查询的数据量？

A.SELECT*FROMOrdersWHERECustomerIDIN(1,2,3);

B.SELECT*FROMOrdersWHERECustomerID=1ORCustomerID=2ORCustomerID=3;

C.SELECT*FROMOrdersWHERECustomerID=1,2,3;

D.SELECT*FROMOrdersWHERECustomerIDIN(1,2,3)ORCustomerID=4;

6.以下哪个SQL语句在执行时可能会出现性能问题？

A.SELECT*FROMCustomersWHERECity=NewYorkORDERBYName;

B.SELECT*FROMCustomersWHERECity=NewYorkANDNameLIKEA%;

C.SELECT*FROMCustomersWHERECity=NewYorkORDERBYNameDESC;

D.SELECT*FROMCustomersWHERECity=NewYorkANDName=John;

7.以下哪个SQL语句可以避免笛卡尔积？

A.SELECT*FROMEmployees,Departments;

B.SELECT*FROMEmployeesINNERJOINDepartmentsONEmployees.DepartmentID=Departments.DepartmentID;

C.SELECT*FROMEmployees,DepartmentsWHEREEmployees.DepartmentID=Departments.DepartmentID;

D.SELECT*FROMEmployeesJOINDepartmentsONEmployees.DepartmentID=Departments.DepartmentID;

8.以下哪个SQL语句可以减少查询的数据量？

A.SELECT*FROMOrdersWHERECustomerIDI