Computer Science
(i) Give one difference between alternate key and candidate key.
(ii) Sartaj has created a table named Student in MYSQL database, SCHOOL:
- rno(Roll number )- integer
- name(Name) - string
- DOB (Date of birth) – Date
- Fee – float
Note the following to establish connectivity between Python and MySQL:
- Username - root
- Password - tiger
- Host - localhost
Sartaj, now wants to display the records of students whose fee is more than 5000. Help Sartaj to write the program in Python.
Answer
(i) One difference between alternate key and candidate key:
| Alternate Key | Candidate Key |
|---|---|
| A candidate key is a set of attributes (columns) in a table that uniquely identifies each record or row. | An alternate key is a set of attributes (columns) in a table that uniquely identifies each record but is not designated as the primary key. |
(ii)
import mysql.connector as mysql
con1 = mysql.connect(host = "localhost",
user = "root",
password = "tiger",
database = "SCHOOL")
mycursor = con1.cursor()
query = "SELECT * FROM student WHERE fee > {}".format(5000)
mycursor.execute(query)
data = mycursor.fetchall()
for rec in data:
print(rec)
con1.close()
Related Questions
Meticulous EduServe is an educational organization. It is planning to setup its India campus at Chennai with its head office at Delhi. The Chennai campus has 4 main buildings – ADMIN, ENGINEERING, BUSINESS and MEDIA.
Block to Block distances (in Mtrs.)
From To Distance ADMIN ENGINEERING 55 m ADMIN BUSINESS 90 m ADMIN MEDIA 50 m ENGINEERING BUSINESS 55 m ENGINEERING MEDIA 50 m BUSINESS MEDIA 45 m DELHI HEAD OFFICE CHENNAI CAMPUS 2175 km Number of computers in each of the blocks/Center is as follows:
block/center Number of computers ADMIN 110 ENGINEERING 75 BUSINESS 40 MEDIA 12 DELHI HEAD 20 (a) Suggest and draw the cable layout to efficiently connect various blocks of buildings within the CHENNAI campus for connecting the digital devices.
(b) Which network device will be used to connect computers in each block to form a local area network?
(c) Which block, in Chennai Campus should be made the server? Justify your answer.
(d) Which fast and very effective wireless transmission medium should preferably be used to connect the head office at DELHI with the campus in CHENNAI?
(e) Is there a requirement of a repeater in the given cable layout? Why/ Why not?
(i) Differentiate between r+ and w+ file modes in Python.
(ii) Consider a file, SPORT.DAT, containing records of the following structure: [SportName, TeamName, No_Players]
Write a function, copyData(), that reads contents from the file SPORT.DAT and copies the records with Sport name as “Basket Ball” to the file named BASKET.DAT. The function should return the total number of records copied to the file BASKET.DAT.
(i) How are text files different from binary files?
(ii) A Binary file, CINEMA.DAT has the following structure:
{MNO:[MNAME, MTYPE]}
Where
MNO – Movie Number
MNAME – Movie Name
MTYPE is Movie TypeWrite a user defined function, findType(mtype), that accepts mtype as parameter and displays all the records from the binary file CINEMA.DAT, that have the value of Movie Type as mtype.
(i) Define the term Domain with respect to RDBMS. Give one example to support your answer.
(ii) Kabir wants to write a program in Python to insert the following record in the table named Student in MYSQL database, SCHOOL:
- rno(Roll number )- integer
- name(Name) - string
- DOB (Date of birth) – Date
- Fee – float
Note the following to establish connectivity between Python and MySQL:
- Username - root
- Password - tiger
- Host - localhost
The values of fields rno, name, DOB and fee has to be accepted from the user. Help Kabir to write the program in Python.