week 3
Learning Aims and Objectives:
Aim: In this week's page, students will learn the.
Objectives:
1. By the end of this week's page students will be able to.
2. By the end of the week's page students will be able to.
3. By the end of the week's page students will be able to .
4. By the end of the week's page students will be able to
5. By the end of the week's page students will be able to.
A3 Normalisation
The role of normalisation to develop efficient data structures:
Normailistaion is a process that is vital to the overall success of a database. In most situations databases are created out of necessity to store data that has already been created or gathered, the database is a tool to provide better access and use to the data to essentially turn it into useful information.
When provided with the raw data a process of normalisation is required to be undertaken to find out how best to store the data without allowing for un-necessary duplication or redundancy, as not only could this lead to confusion but also to increased file sizes of a database, which could, in turn, slow down its ability to retrieve data and information.
https://www.bbc.co.uk/bitesize/guides/zvq634j/test
• anomalies – update, insertion, deletion
• primary keys, foreign keys, composite keys
As mentioned in earlier lessons the use of keys be them primary, foreign or composite as core to the success of a database, in the normalisation process we will identify the primary key within the data sets that are gathered/gained/provided and then move to split them out in to their composite tables, then we will be able to see the links between the tables where they happen naturally, for example, a person living at the same address could be done using foreign keys for the house as a number of people can live in the same place.
• indexing
Referential Integrity
Referential integrity is a database concept that is used to create and maintain logical relationships between tables.
Usually, referential integrity is made up by the combination of primary keys and foreign keys within database tables.
The main purpose of the referential integrity concept is that it does not allow to add any record in a table that contains the foreign key unless the reference table containing a corresponding primary key.
If any record in the referenced table (i.e. the table who contain primary key) is deleted, all the corresponding records in the referencing table will be deleted for the referential integrity.
• data dictionary – tables, fields, data types, validation
Data dictionarty's are important to the developer to ensure that the correct structure of the database is created. this is essentially an instruction manual to a developer to create the correct input types to the fields in a database system, for example, the use of the number for the age of an individual and that the field length of this should only be at most 3. I do not know of anyone that is older than 999 do you!!?
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Validation |
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Cascading update
The cascade update feature of a database will enable the user to update a database value of a primary key in its table and for the associated foreign key in other linked tables to be updated. For example, the primary key in a table for bikes, the id was originally just the number, so 1,2, 3,4, the company have now updated the field to include 1000 before the primary key number so the record will look like 10001, 10002, 10003, 10004 and so on.
Deletion techniques
Joins, Unions, and Intersects
Stages of normalisation:
o un-normalised form (UNF) : - UNF is completely raw, this is where the data and the headings that they are under are in a single "table" ASSIGNMENT TIP (Look for the ID's)
o first normal form (1NF) : - 1st normal form is when the data is where you try to create individual table entities, grabbing the IDs as an indication to the tables will help
o second normal form (2NF) : - 2nd NF is where the duplication is attempted to be removed, it may be that another table may need to be created, this will require a new id to be created.
o third normal form (3NF) : - 3rd NF should provide a completely normalized version of the tables and entities within them including the required foreign keys that would need to be in the tables to establish the links.
Exercise 1
Exercise 2Exercise 3
Last Updated
2024-09-04 14:23:59
Links to Learning Outcomes |
Links to Assessment criteria |
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AO1 Demonstrate knowledge of database development terminology, standards, concepts and processes AO2 Apply knowledge and understanding of database development terminology, standards, concepts and processes to create a software product to meet a client brief
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English
Reading: Read and understand texts, selecting material appropriate to purpose, collating from different sources and making comparisons and cross-references as appropriate.
Organising Information: Organise information and ideas into structured and sequenced sentences, paragraphs and whole texts, using a variety of linguistic and structural features to support cohesion and overall coherence.
Maths
Using Numbers: Counting, Place value, adding and subtracting, multiplying and dividing.
Using numbers: Written or mental methods, using a calculator, rounding and estimating, problem solving
Analysis of information: Interpreting Results, Drawing conclusions from data, Comparing data
How 2's Coverage
Anonymous Assessment - Learners assess an anonymous piece of work containing deliberate mistakes against given success criteria.
Peer Assessment of Independent Work - Learners work in groups to assess each other's work and make recommendations for improvement.
Anonymous Assessment - Learners assess an anonymous piece of work containing deliberate mistakes against given success criteria.
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