Fundamentals of Databases

Question 1

What is a entity?

Answer 1

A category of object, person, event or thing of interest about which data needs to be recorded.

Question 2

What is a attribute?

Answer 2

An identifier of what data is stored in the entity.

Question 3

What is a primary key?

Answer 3

A attribute that uniquely identifies a particular record.

Question 4

What is a composite primary key?

Answer 4

When two or more attributes are used to uniquely identify a record.

Question 5

What are the possible relationships between databases?

Answer 5

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

Question 6

What is a foreign key?

Answer 6

When the primary key of one table is in another table.

Question 7

What is a flat-file database?

Answer 7

Where only one table holds all the data.

Question 8

What is a relational database?

Answer 8

Where data is stored on multiple tables.

Question 9

What conditions have to be met for a data to be 1st normalised form ?

Answer 9

No repeating attributes
All attributes are atomic.

Question 10

What conditions have to be met for a data to be 2nd normalised form?

Answer 10

In 1NF
No partial dependencies on composite key.

Question 11

What conditions have to be met for a data to be 3rd normalised form?

Answer 11

In 2NF
No non-key dependencies

Question 12

What is the SQL statement to return certain items?

Answer 12

SELECT fields
FROM tables
WHERE conditions

Question 13

What is the SQL statement to organise data returned?

Answer 13

ORDER BY (ASC/ DESC)

Question 14

What does the SQL statement LIKE do?

Answer 14

WHERE … LIKE …
Selects data that starts/ ends with a certain character. (St*)

Question 15

What does the SQL statement BETWEEN do?

Answer 15

WHERE … BETWEEN … AND …
Returns data values between the values given.

Question 16

How do you return data from two tables?

Answer 16

FROM table1, table2
WHERE table1.primarykey = table2.foreignkey

Question 17

What is the SQL statement to combine data from multiple tables?

Answer 17

JOIN table
ON primarykey = foreignkey
WHERE conditions

Question 18

What is the SQL statement to create a new table?

Answer 18

CREATE TABLE name
(data)

Question 19

How do you specify data values when creating a new table?

Answer 19

userID CHAR(6) PRIMARY KEY, NOT NULL
name VARCHAR(num)

Question 20

How do you specify a foreign key when creating a new table?

Answer 20

FOREIGN KEY name REFERENCES name(table)

Question 21

What are the possible data types for a table? (8)

Answer 21

CHAR
VARCHAR
BOOLEAN
INTEGER
FLOAT
DATE
TIME
CURRENCY

Question 22

What is the SQL statement to add a new attribute to a table?

Answer 22

ALTER TABLE table
ADD attribute

Question 23

What is the SQL statement to delete an attribute in a table?

Answer 23

ALTER TABLE table
DROP attribute

Question 24

What is the SQL statement to add a new record into a table?

Answer 24

INSERT INTO table(attributes)
VALUES (values)

Question 25

What is the SQL statement to change a record in a table?

Answer 25

UPDATE table
SET new values
WHERE record

Question 26

What is the SQL statement to remove a record from a table?

Answer 26

DELETE FROM table
WHERE record