Databases

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

• All transactions must be recorded on the database

• The database is able to be used by anybody

• If somebody drops the storage drive with the database on, it will still function

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

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

• Field
• File
• Record
• Table

Normalisation is:

• Removing all necessary data from a database

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

• Putting fields from different tables into one big database

Write the code for the following : Return all movies with the word love.

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

Which data type would be most suitable for Length?

• Integer

• Float/Double

• Boolean

• String

To be in 2NF:

• Any field not relating to the PK is placed in a separate table
• The records all relate easily
• Each table has a foreign key
• There are no redundancies

What is a database?

• A piece of software to do calculations
• A device to load information onto the computer.
• A structured collection of information
• A calculator

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

• SELECT city WHERE humidity = 95

• SELECT city FROM weather WHERE humidity = 95

• SELECT humidity = 89 FROM weather

• SELECT city FROM weather

A gym has a database with all their members they want to include email addresses in the database, what will they do?

• Add a record
• Add a field
• Edit a record
• Delete a field

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

• A transaction that has been bad must be placed in isolation until it knows what it has done wrong. Usually 1 minute per year after it has been created.

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

• If somebody is accessing the same record, they must be stopped

• Records are put on their own for identification