Organising a database to remove repeated entries and increase the accuracy of the data

What is an atomic field?

A field that contains only one item of data

What is a foreign key?

A primary key of one table that appears in another table

When you normalize a relation by breaking it into two smaller relations, what must you do to maintain data integrity?

Create a primary key(s) for the new relation

What does Normalisation allow a database designer to do?

Design their database efficiently, removing the chance of redundancy and inaccuracies.

Each non-key field relates to the primary key

To be in 2NF, what must be done?

Any field not relating to the PK is placed in a separate table.

To be in 3NF, what is required?

Records do not depend on anything other than the table's PK

What is a primary key?

Is a unique identifier for the table. It cannot be null.

An ER diagram shows relationships between:

Tables in a relational database.

Why is the statement 'Many users access many servers' not a good inclusion in an ER diagram?

It creates duplicates and therefore redundancy.

What is the purpose of *?

Selects ALL fields from the table

Return the name and genre of each movie with an imdb_rating greater than 5 and year greater than 2012.

SELECT name, genre FROM movies WHERE imdb_rating > 5 AND year > 2012;

Write the code to return all movies with the word love.

SELECT * FROM movies WHERE name LIKE ‘%love%’;

In ACID, A stands for Atomicity. But what does that mean?

A transaction must be processed in its entirety or not at all

In ACID, the C stands for consistency. What does this mean?

A transaction cannot break any of the validation rules which maintain the integrity of the database

The I in ACID stands for isolation. What does this mean?

No other transaction can be completed until the current transaction is completed even if they have to be completed concurrently.

The D in ACID stands for durability. What does this mean?

Once a transaction has been committed, the transactions dependent on this will be completed even if there is a power cut.

With SQL, how do you select all the records from a table named “Persons” where the value of the column “FirstName” ends with an “a”?

SELECT * FROM Persons WHERE FirstName LIKE ‘%a’

How can you change “Hansen” into “Nilsen” in the “LastName” column in the Persons table?

UPDATE Persons SET LastName=’Nilsen’ WHERE LastName=’Hansen’

SQL query to find all the cities whose humidity is 95.

SELECT city FROM weather WHERE humidity = 95

SQL query to find the temperature in increasing order of all cities.

SELECT city, temperature FROM weather ORDER BY temperature

Find the name of those cities with temperature and condition whose condition is either sunny or cloudy but temperature must be greater than 70.

SELECT city, temperature, condition FROM weather WHERE condition = ‘sunny’ OR condition = ‘cloudy’ AND temperature > 70

Find the names of these cities with temperature and condition whose condition is neither sunny nor cloudy.

SELECT city, temperature, condition FROM weather WHERE condition NOT IN (‘sunny’, ‘cloudy’)

Databases Flashcards

Student preview

50 questions

Show all answers

1.

FLASHCARD QUESTION

Front

What is a database?

Back

A structured collection of information

2.

FLASHCARD QUESTION

Front

What describes a relational database?

Back

There are two or more tables that are linked using the primary keys

3.

FLASHCARD QUESTION

Front

The individual information about each member in a sports club is called a:

Back

Record

4.

FLASHCARD QUESTION

Front

What would the secretary do with the record for a member who has decided to resign from the Sports Club?

Back

Delete the record

5.

FLASHCARD QUESTION

Front

How will the Sports Club add a new member's details to the database?

Back

Add a new record

6.

FLASHCARD QUESTION

Front

The whole database is called:

Back

The file

7.

FLASHCARD QUESTION

Front

One specific piece of information about a person or thing is called:

Back

Field

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