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Databases - lesson 6
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- Was it difficult?
- Easier than you thought it would be?
- Was there anything that you felt unprepared to answer?
Answers
Let's swap papers and peer assess.
Mock paper
We will be completing a collection of actual questions that have featured on previous exam papers.
Advantages
Learning Objectives:
- Simple to implement
- We can use search algorithms such as binary search to find records quickly
Organising data
Disadvantages
Sequential file organisation
- The file needs to be recreated each time a record is added as it needs to be inserted in the correct place.
Sequential data is organised into some kind of order based on a particular field
- To understand how the advantages and disadvantages of sequential, serial and indexed storage.
- To apply your knowledge in completing past questions from A451.
I could organise a list of addresses by the house number for example
Indexed file storage
Starter -
end of topic
To improve the performance of access to a sequential file we can create an index.
Advantages
Mini plenary
Faster than searching sequentially once the index has been set up
Disadvantages
It can take longer to add new records as the record will also need to be added to the index too.
An index is a separate data structure which groups records.
Like the index in a catalogue we use them to look where the data is held rather than to look for the data itself.
Complete the end of topic starter activity. This focuses on data validation
Databases
(5 mins)
Serial files
Serial files are stored in the order than they were entered into the database. This means that the first records to be entered are stored at the top of the database and the last entries are stored at the bottom.
This can cause problems when searching for data as the only method available for us to use is a linear search.