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Question
______ command is used to remove the primary key from a table in SQL.
Options
update
remove
alter
drop
Solution
Alter command is used to remove the primary key from a table in SQL.
Explanation:
The alter table command is used to remove the primary key from a table in SQL.
Syntax to remove the primary key:
ALTER TABLE table_name DROP PRIMARY KEY;
So, the correct answer is Alter.
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RELATED QUESTIONS
Each table comprises of ______ and ______.
Case Based
Consider the table STUDENT with the following detail.
| STU_ID | NAME | STREAM | MARKS | CLASS |
| 1. | Aditya | Science | 87.5 | 12A |
| 2. | Vikram | Commerce | 88.7 | 12B |
| 3. | Astha | Humanities | 76.8 | 12C |
| 4. | Varsha | Science | 79.5 | 12A |
| 5. | Kanishka | Science | 77.9 | 12A |
| 6. | Anand | Commerce | 86.7 | 12B |
Now answer the question given below:
Command to select all Science students from the table STUDENT
Case Based
Consider the table STUDENT with the following detail.
| STU_ID | NAME | STREAM | MARKS | CLASS |
| 1. | Aditya | Science | 87.5 | 12A |
| 2. | Vikram | Commerce | 88.7 | 12B |
| 3. | Astha | Humanities | 76.8 | 12C |
| 4. | Varsha | Science | 79.5 | 12A |
| 5. | Kanishka | Science | 77.9 | 12A |
| 6. | Anand | Commerce | 86.7 | 12B |
Now answer the question given below:
Delete records that belongs to 'Humanities' stream.
Which of the following command is used to remove a relation from an SQL database?
Which of the following is not an RDBMS?
Which of the following are included in defining a schema?
What is not true with respect to the create table statement?
What statement will you give to view the structure of a table?
How will you add a primary key to a relation?
How will you add two columns coll and col2(composite key) as primary key to a relation?
How will you add a foreign key to a relation?
Which statement is used to remove a table from the database?
Differentiate between the following statement:
ALTER and UPDATE
A shop called Wonderful Garments which sells school uniforms maintains a database SCHOOLUNIFORM as shown below. It consisted of two relations - UNIFORM and COST. They made UniformCode the primary key for UNIFORM relations. Further, they used UniformCode and Size to be composite keys for COSTrelation. By analyzing the database schema and database state, specify SQL queries to rectify the following anomalies.
- M/S Wonderful Garments also keeps handkerchiefs of red colour, medium size of Rs. 100 each.
- INSERT INTO COST (UCode, Size, Price) values (7, 'M', 100);
When the above query is used to insert data, the values for the handkerchief without entering its details in the UNIFORM relation are entered. Make a provision so that the data can be entered in the COST table only if it is already there in the UNIFORM table. - Further, they should be able to assign a new UCode to an item only if it has a valid UName. Write a query to add appropriate constraints to the SCHOOLUNIFORM database.
- Add the constraint so that the price of an item is always greater than zero.
Suppose your school management has decided to conduct cricket matches between students of Class XI and Class XII. Students of each class are asked to join any one of the four teams – Team Titan, Team Rockers, Team Magnet, and Team Hurricane. During summer vacations, various matches will be conducted between these teams. Help your sports teacher to do the following:
- Create a database “Sports”.
- Create a table “TEAM” with the following considerations:
i) It should have a column TeamID for storing an integer value between 1 to 9, which refers to the unique identification of a team.
ii) Each TeamID should have its associated name (TeamName), which should be a string of length not less than 10 characters. - Using table level constraint, make TeamID the primary key.
- Show the structure of the table TEAM using a SQL statement.
- As per the preferences of the students four teams were formed as given below. Insert these four rows in the TEAM table:
Row 1: (1, Team Titan)
Row 2: (2, Team Rockers)
Row 3: (3, Team Magnet)
Row 3: (4, Team Hurricane) - Show the contents of the table TEAM using a DML statement.
- Now create another table MATCH_DETAILS and insert data as shown below. Choose appropriate data types and constraints for each attribute.
| Table: MATCH_DETAILS | |||||
| MatchID | MatchDate | FirstTeamID | SecondTeamID | FirstTeamScore | SecondTeamScore |
| M1 | 2018-07-17 | 1 | 2 | 90 | 86 |
| M2 | 2018-07-18 | 3 | 4 | 45 | 48 |
| M3 | 2018-07-19 | 1 | 3 | 78 | 56 |
| M4 | 2018-07-19 | 2 | 4 | 56 | 67 |
| M5 | 2018-07-18 | 1 | 4 | 32 | 87 |
| M6 | 2018-07-17 | 2 | 3 | 67 | 51 |
Using the CARSHOWROOM database given in the chapter, write the SQL queries for the following:
- Add a new column Discount in the INVENTORY table.
- Set appropriate discount values for all cars keeping in mind the following:
(i) No discount is available on the LXI model.
(ii) VXI model gives a 10 percent discount.
(iii) A 12 percent discount is given on cars other than the LXI model and VXI model. - Display the name of the costliest car with the fuel type “Petrol”.
- Calculate the average discount and total discount available on Baleno cars.
- List the total number of cars having no discount.
______ is a non-key attribute, whose values are derived from the primary key of some other table.
To establish a connection between Python and SQL databases, connect() is used. Which of the following arguments may not necessarily be given while calling connect()?
The code given below reads the following record from the table named student and displays only those records that have marks greater than 75:
- RollNo - integer
- Name - string
- Clas - integer
- Marks - integer
Note the following to establish connectivity between Python and MYSQL:
- Username is root.
- The password is the tiger.
- The table exists in an MYSQL database named school.
Write the following missing statements to complete the code:
Statement 1 - to form the cursor object
Statement 2 - to execute the query that extracts records of those students whose marks are greater than 75.
Statement 3 - to read the complete result of the query (records whose marks are greater than 75) into the object named data, from the table student in the database.
import mysql.connector as mysql
def sql_data():
con1=mysql.connect(host="localhost",user="root",password="tiger", database="school")
mycursor=_______________ #Statement 1
print("Students with marks greater than 75 are :")
_________________________ #Statement 2
data=__________________ #Statement 3
for i in data:
print(i)
print()Write the command to view all databases.
The code given below deletes the record from the table employee, which contains the following record structure:
E_code - StringE_name - StringSal - IntegerCity - String
Note the following to establish connectivity between Python and MySQL:
- Username is
root - Password is
root - The table exists in a MySQL database named
emp. - The details
(E_code, E_name, Sal, City)are the attributes of the table.
Write the following statements to complete the code:
Statement 1 – to import the desired library.
Statement 2 – to execute the command that deletes the record with E_code as 'E101'.
Statement 3 – to delete the record permanently from the database. ____________
import ____________ as mysql #Statement1
def delete():
mydb=mysql.connect(host="localhost",use r="root",
passwd="root",database="emp")
mycursor=mydb.cursor()
____________ #Statement 2
____________ #Statement 3
print ("Record deleted") Ms Shalini has just created a table named “Employee” containing columns Ename, Department and Salary. After creating the table, she realized that she has forgotten to add a primary key column in the table. Help her in writing an SQL command to add a primary key column EmpId of integer type to the table Employee.
Thereafter, write the command to insert the following record in the table:
EmpId- 999
Ename- Shweta
Department: Production
Salary: 26900