sql

Question 1

What is a flat-file database?

Answer 1

A database made up of one table

Question 2

What is a relational database?

Answer 2

A database containing more than one table

Question 3

What is an entity?

Answer 3

a collection of all related records

Question 4

What is a primary key?

Answer 4

a unique value in a table e.g. teacher_ID

Question 5

What is a secondary key?

Answer 5

data that can be used for a specific search e.g.teacher_name

Question 6

What is a foreign key?

Answer 6

a field that references the primary key of another table

Question 7

What are the 3 types of relationships?

Answer 7

one-to-one
one-to-many
many-to-many

Question 8

Why is a many-to-many relationship a potential problem?

Answer 8

it will be difficult to reassemble the data

Question 9

How do you select all the data from a table?

Answer 9

SELECT*

FROM table_name

Question 10

How do you select specific data from a table?

Answer 10

SELECT attribute1, attribute2

FROM table_name

Question 11

How do you select data depending on the value of an attribute?

Answer 11

SELECT*
FROM table_name
WHERE attribute=value

Question 12

How do you order data by ascending order?

Answer 12

SELECT*
FROM table_name
ORDER BY attribute ASC

Question 13

How do you order data by descending order?

Answer 13

SELECT*
FROM table_name
ORDER BY attribute DESC

Question 14

How do you select data from 2 tables?

Answer 14

SELECT table1_attribute,
table2_attribute
FROM table1, table2

Question 15

How do you select data and join 2 tables?

Answer 15

SELECT*
FROM table1, table2
WHERE
table1attribute+table2attribute

Question 16

What are the advantages of a flat-file database?

Answer 16

all records stored in one place
easy to understand
easy to set up
simple sorting of records
simply view or extract records
every day things like business contacts can be stored and used

Question 17

What are the disadvantages of a flat-file database?

Answer 17

potential duplication
non-unique records
harder to update
inefficient
harder to change data format
poor at complex queries
poor at limiting access

Question 18

What are the advantages of relation databases?

Answer 18

no multiple record changes needed
more efficient
simple to delete or modify details
complex queries can be carried out
better security
cater for future requirements