Practice for Test 1 (not counted for credit, but to help you prepare) Time allowed: 1 hour 15 minutes

Transcription

1 p.1 of 8 INFS 4240/6240 (Section A) Database Management System Fall 2018 Practice for Test 1 (not counted for credit, but to help you prepare) Time allowed: 1 hour 15 minutes Q.1(a) Q.1(b) Q.1(c) Q.1(d) Q.1(e) Q.1(f) Q.1(g) Q.2(a) Name: Sample Answers Q.2(b) Open Book, Open Notes, including web access. Consultation with other people not allowed. Answer all questions. Answer in the space provided. Please give a good effort to make your writing readable. Read each of the questions carefully before working on it. Q.2(c) 5 5 Total

2 p.2 of 8 Q.1 We have access to a simple personnel database for a certain company with 26 employees in 4 departments. The four departments are: Executive, Accounting, Sales, and Engineering. The personnel database consists of one table, with the schema illustrated in the following. Employee( EmpNo, EmpName, Dept, Gender, Salary ). The Employee table has 5 columns: EmpNo is a unique number to identify each employee and it constitutes the whole primary key; EmpName is the name of the employee; Dept is the name of the department the employee belongs to. (Every employee must belong to exactly one department, null value is not allowed.) Gender is the employee s gender: M for Male and F for Female; Salary is employee s salary in dollars and cents. Answer the following questions Q.1(a) to Q.1(g). [75 points total: (a) 15 points, (b) to (g) 10 points each.] Q.1(a) Write down an SQL statement to create the Employee table, with the constraints as specified above. You may also assume any reasonable use of datatypes, including these: Number for EmpNo, Text for EmpName and Dept, single character length text string for Gender and Currency or Number for Salary. Be sure to cover the required constraints as stated above. (15 points) CREATE TABLE Employee (EmpNo number Primary Key, EmpName text, Dept text not null, Gender char(1), Salary currency);

3 p.3 of 8 Q.1 We are provided with access to the database, both MS Access and Oracle. If you want to use MS Access, copy the file at P:\wu\DMT1\Q1Emp.accdb to your computer. The database contains the table Employee already populated with data for your use. If you use Oracle, sign on with SQL*Plus using your user-id@infs4240 and your password, refer to the table as wu.employee in your SQL statement. Q.1(b) Write an SQL statement to list all employees of the Accounting Department: list EmpNo and EmpName. List the result in alphabetical order by the Employee s Name. The SQL statement should make sure that the results listed contains no duplicate entries for any data situation. Write down the SQL statement below, along with the result you get from the SQL statement. (10 points). SELECT EmpNo, EmpName WHERE Dept = Accounting ORDER BY EmpName; Q1B EmpNo EmpName 22 Vincent 23 William 24 Xena 25 Yvonne 26 Zoe

4 p.4 of 8 Q.1(c) Write an SQL statement to determine the maximum salary paid to an employee. List just the salary amount. Write down the SQL statement below, along with the result from the SQL statement. (10 points) SELECT MAX(Salary) ; Q1C Expr1000 $140, Q.1(d) Knowing the maximum salary from Q1.(c) above, write the SQL statement to list all the employees at the maximum salary. List the employee s name (EmpName), and the department name (Dept), and the Salary. Write down the SQL statement below, along with the result from the SQL statement. (10 points) SELECT EmpName, Dept, Salary WHERE Salary = ; Or (if you may use a sub-query ) SELECT EmpName, Dept, Salary WHERE Salary = (Select MAX(Salary) from Employee); Q1D EmpName Dept Salary Aaron Executive $140, Charles Executive $140,000.00

5 p.5 of 8 Q.1(e) Write an SQL statement to determine the number of employees and the average salary in the Sales Department: list the number of employees and then the average salary together using one SQL statement. Write down the SQL statement, along with the result from the SQL statement. (10 points) SELECT Count(*), Avg(Salary) WHERE Dept = Sales ; Q1E Expr1000 Expr $49, Q.1(f) Write an SQL statement to list the number of employees, and the average salary for every department: list the department name (Dept), the number of employees, and the average salary. List the result in descending order of the average salary in the department. Write down the SQL statement below, and show the result from the SQL statement. (10 points) SELECT Dept, Count(*), Avg(Salary) GROUP BY Dept ORDER BY Avg(Salary) DESC; Dept Q1F Expr1001 Expr1002 Executive 4 $119, Engineering 7 $56, Accounting 5 $51, Sales 10 $49,500.00

6 p.6 of 8 Q.1(g) Write an SQL statement to list the number of employees, and the average salary for those departments in which average salary is higher than $55,000: list the department name (Dept), the number of employees, and the average salary. List the result in alphebetical order by the department name. Write down the SQL statement below, and show the result from the SQL statement. (10 points) SELECT Dept, Count(*), Avg(Salary) GROUP BY Dept HAVING Avg(Salary) > ORDER BY Dept ASC; Dept Q1G Count(*) Avg(Salary) Engineering 7 $56, Executive 4 $119,250.00

7 p.7 of 8 Q.2 In a certain small college summer program, each course offered in the 8 weeks summer program period meets once a week, Monday to Friday, and for 3 hours each period. The following table ASSIGNMENT keeps track of the classroom assignment for the courses. Each course is identified by course number CNum. Bldg and Room are the Building name and Room number respectively, indicating the classroom assigned to the course. Day specifies which day of the week the class meets. Each class meets for 3 hours. Note that StartTime must be 9am, 12noon, 3pm, or 6pm. Enroll specifies the number of students enrolled in the course. The following illustrates what the table may look like. ASSIGNMENT CNum Bldg Room Day StartTime Enroll 2150 Hale 302 WED 9am Hopeman 401 FRI 12noon Wheatley 119 TUE 3pm 22 Answer the questions Q2.(a),(b),(c) [25 points total: (a),(b) 10 points, (c) 5 points] Note that the SQL statements should be written for the schema, so that the statements should execute correctly with any possible data situation. The data shown in the above is for the purpose of illustration only. We should not need to have the database to write the SQL statements. Q.2(a) Write an SQL statement to list all the courses with classes meeting in Hale on Monday (MON) starting at 9am. List the course number (CNum), the room number (Room) for the class and the number of students enrolled (Enroll). Order the result by room number. Just write down the SQL statement; NO need to show data result. (The result would depend on the specific data situation. The SQL statement should work correctly according to the schema, and for any data situation.) (10 points) SELECT CNum, Room, Enroll FROM ASSIGNMENT WHERE Bldg = Hale AND Day = MON AND StartTime = 9am ORDER BY Room;

8 p.8 of 8 Q.2(b) A classroom must be able to accommodate the number of students as enrolled. Write an SQL statement to find the maximum number of students that may be in each classroom for any course in Hale center. List the room number (Room) and the maximum number of students (max of Enroll) that may be there, presenting the result order by room number. Write down just the SQL statement. (10 points) SELECT Room, max(enroll) FROM ASSIGNMENT WHERE Bldg = Hale GROUP BY Room ORDER BY Room; Q.2(c) The primary key for the ASSIGNMENT table has one column CNum. Find another candidate key for the table which may to used to serve as a secondary key. (NOTE: A candidate key for a table is a minimal collection of columns of the table such that no two rows in the table may have exact same data values under those columns, so that it may serve as key. It is a minimal collection because if we remove any column in the collection, it can no longer serve as a key.) (5 points) Another candidate key consists the following 4 columns: Bldg, Room, Day, StartTime Each row identifies a course (by its unique CNum); no two courses can meet in the same place at the same time. Therefore, no two rows will have same data values under these columns. More, the collection cannot be reduced in any way. SQL to create the table, using it as a Secondary Key CREATE TABLE ASSIGNMENT (CNum text Primary Key, Bldg text, Room number, Day text, StartTime text, Enroll number, Unique(Bldg,Room,Day,StartTime) ); Note then the table will NOT allow incorrect data entry to have two different courses mistakenly assigned a conflicting schedule class meeting at the same place and same time. The Secondary Key will prevent such insertion of data, with the error message Violation of Secondary Key constraint. - End -