Databases and SQL

Question 1

What is a flat file database?

Answer 1

A flat file database is a database of just one table.
It’s an organised computerised system that makes it easy to search, select and store information. It stores information until specifically deleted.

Question 2

What is a relational database?

Answer 2

A relational database is a structured database that is made up of more than one table. It allows data to be separated and connected across several tables.

Question 3

What is a primary key?

Answer 3

A primary key is an unique identifier for each record. It uniquely identifies a record in one table and a table can only have one primary key.

Question 4

What is a table?

Answer 4

A table is a collection of record for a specific theme.

Question 5

What is a field?

Answer 5

A field is categories for each piece of data in a table.

Question 6

Give some examples of a field.

Answer 6

First name
Surname
Student ID

Question 7

What is a record?

Answer 7

A record is a row of data for one object, person, or place.

Question 8

Why can data redundancy be a problem?

Answer 8

Data redundancy can be a problem because data can be repeated in a database table, and it makes the database file much larger than it needs to be.

Question 9

Why can data inconsistency be a problem?

Answer 9

Data inconsistency can be a problem because the more redundant data there is, the more likelihood there is that errors are introduced and that some of that data will be inconsistent. This would create differences in the data stored on a database.

Question 10

What is a foreign key?

Answer 10

A foreign key is a primary key from one table that appears in another table to link the two together.

Question 11

Why might the primary key for one table, not be the same primary key in another table?

Answer 11

A primary key provides a mechanism for ensuring that the rows in a table are unique. Other columns might also contain unique values, but a table can contain only one primary key. Because the primary key must be able to identify each row, no columns that participate in a primary key can contain NULL values.

Question 12

What are comparison operators?

Answer 12

= - Equal to
> - Greater than
< - Less than
>= - Greater than or equal to
<= - Less than or equal to
<> OR =! - Not equal to

Question 13

Logical Operators:

AND

Answer 13

AND - TRUE if both conditions are TRUE

Question 14

Logical Operators:

BETWEEN

Answer 14

BETWEEN - TRUE if the range is within the comparisons

Question 15

Logical Operators:

OR

Answer 15

OR - TRUE if any of the conditions are TRUE

Question 16

Different data types:

Integer

Answer 16

Integer- a whole number

Question 17

Different data types:

Real

Answer 17

Real- a number with a decimal point

Question 18

Different data types:

Text

Answer 18

Text- a string of variable length

Question 19

CREATING A DATABASE:

Question 20

There are also a number of tick boxes for each field:

Answer 20

NN (Not Null) this field cannot be left blank

Question 21

There are also a number of tick boxes for each field:

Answer 21

PK (Primary Key) this field is the primary key, the unique
identifier for the table. This will ensure it is unique and
cannot be left blank

Question 22

There are also a number of tick boxes for each field:

Answer 22

Al (Automatic Increment) if this is a number it will add I
onto the last one to generate a new number, usually used
for Primary Key fields

Question 23

There are also a number of tick boxes for each field:

Answer 23

U (Unique) this is used to say the contents need to contain
a unique value and cannot contain any duplicate values.
If you select PK this field does not need to be ticked as PK
already specifies it needs to be set to unique