SQL性能调优试题及答案集锦
姓名：____________________
一、单项选择题（每题2分，共10题）
1.以下哪个SQL语句是错误的？
A.SELECT*FROMemployeesWHEREsalary50000;
B.SELECT*FROMemployeesWHEREdepartment_id=(SELECTdepartment_idFROMdepartmentsWHEREdepartment_name=HR);
C.SELECTdepartment_name,COUNT(*)FROMemployees,departmentsWHEREemployees.department_id=departments.department_idGROUPBYdepartment_name;
D.SELECTdepartment_name,AVG(salary)FROMemployees,departmentsWHEREemployees.department_id=departments.department_idGROUPBYdepartment_name;
2.在SQL中，如何对查询结果进行排序？
A.ORDERBY
B.SORTBY
C.ASC
D.DESC
3.以下哪个SQL语句可以删除名为“employees”的表？
A.DROPTABLEemployees;
B.DELETEFROMemployees;
C.TRUNCATETABLEemployees;
D.DELETETABLEemployees;
4.在SQL中，如何创建一个名为“departments”的表，包含两个字段：department_id（主键）和department_name？
A.CREATETABLEdepartments(department_idINTPRIMARYKEY,department_nameVARCHAR(50));
B.CREATETABLEdepartments(department_idINT,department_nameVARCHAR(50));
C.CREATETABLEdepartments(department_idINTPRIMARYKEY,department_nameVARCHAR(50),department_nameVARCHAR(50));
D.CREATETABLEdepartments(department_idINT,department_nameVARCHAR(50),department_nameVARCHAR(50)PRIMARYKEY);
5.以下哪个SQL语句可以更新名为“employees”的表中名为“salary”的字段？
A.UPDATEemployeesSETsalary=60000WHEREemployee_id=1;
B.UPDATEemployeesSETsalary=60000,employee_id=1;
C.UPDATEemployees,salary=60000WHEREemployee_id=1;
D.UPDATEemployeesSETsalary=60000,employee_id=1,salary=60000;
6.在SQL中，如何创建一个视图，名为“view_employees”，包含字段：employee_id,first_name,last_name，并从名为“employees”的表中查询？
A.CREATEVIEWview_employeesASSELECTemployee_id,first_name,last_nameFROMemployees;
B.CREATEVIEWview_employeesASSELECTemployee_id,first_name,last_nameFROMemployees,departments;
C.CREATEVIEWview_employeesASSELECTemployee_id,first_name,last_nameFROMemployeesWHEREdepartment_id=1;
D.CREATEVIEWview_employeesASSELECTemployee_id,first_name,last_na