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Structured Query Language

Question

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Give a suitable example of a table with sample data and illustrate Primary and Alternate Keys in it.

Solution

Primary Key: Primary key is a set of one or more fields/columns of a table that uniquely identify a record in the database table. It cannot accept null, duplicate values. Only one Candidate Key can be Primary Key.
Alternate key: the Alternate key is a key that can be work as a primary key. Basically, it is a candidate key that currently is not the primary key.
Example: In below table AdmissionNo becomes Alternate Keys when we define RegistrationNo as Primary Key.

Student Registration Table:

RegistrationNo	AdmissionNo	Name	Phone	Gender	DOB
CBSE4554	215647	Mihir Ranjan	9568452325	Male	1992-04-15
CBSE6985	265894	Amita Guha	8456985445	Female	1993-03-24
CBSE5668	458961	Rajesh Singh	9654212440	Male	1992-12-04
CBSE3654	469799	Mohit Patel	7421589652	Male	1992-05-16

Primary Key – Registration Number

Alternate Key – Admission No

Some More Questions From Structured Query Language Chapter

Give a suitable example of a table with sample data and illustrate Primary and Alternate Keys in it.

Consider the following tables CARDEN and CUSTOMER and answer (b) and (c) parts of question:
TABLE: CARDEN

Ccode

CarName

Make

Color

Capacity

Charges

501

A-Star

Suzuki

RED

3

14

503

Indigo

Tata

SILVER

3

12

502

Innova

Toyota

WHITE

7

15

509

SX4

Suzuki

SILVER

4

14

TABLE: CUSTOMER

CCode

Cname

Ccode

1001

Hemant Sahu

501

1002

Raj Lal

509

1002

Feroza Shah

503

1004

Ketan Dhal

502

Write SQL commands for the following statements:

To display the names of all the silver colored

To display name of car, make and capacity of cars in descending order of their sitting

To display the highest charges at which a vehicle can be hired from

To display the customer name and the corresponding name of the cars hired by them

Consider the following tables CARDEN and CUSTOMER and answer (b) and (c) parts of question:
TABLE: CARDEN

Ccode

CarName

Make

Color

Capacity

Charges

501

A-Star

Suzuki

RED

3

14

503

Indigo

Tata

SILVER

3

12

502

Innova

Toyota

WHITE

7

15

509

SX4

Suzuki

SILVER

4

14

TABLE: CUSTOMER

CCode

Cname

Ccode

1001

Hemant Sahu

501

1002

Raj Lal

509

1002

Feroza Shah

503

1004

Ketan Dhal

502

Give the output of the following SQL queries:

SELECT COUNT(DISTINCT Make) FROM CARDEN;

SELECT MAX(Charges),MIN(Charges) FROM CARDEN;

SELECT COUNT(*),Make FROM CARDEN;

SELECT CarName FROM CARDEN WHERE Capacity=4;

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