Flashcards
Chapter 5
Flashcards do conjunto (11)
- 11. What is a table made up from? 2. What is the data structure? 3. to be called a table what requirements must it meet?1. Records which are made up of fields which are made up of characters.
2. rows and columns.
3. - must have a unique field name
- each field / column must have a unique name
- each record must be unique
- each data item must only contain a single data item - 21. What is a record? 2. What is a field? 3. What is the most important key in a table?1. A record is a single row within a table.
2. A field is an individual data item within a record.
3. the primary key - 31. what does the primary key do? 2. what are the two possible types of primary key? 3. what is a single primary key?1. allows each record to be uniquely identifiable.
2. compound and simple.
3. made up of a single field only like ID. - 41. what is a compound primary key? 2. why is a foreign key used?1. combines more than one field to make a unique value.
2. to link tables together. it is a field in one table that is linked to a primary key in another table. (the data types linked must be the same) - 5If a table is in 1NF what does it consist of?- atomic data.
- does not contain repeating data.
- each row is uniquely identifiable.
- each field name must be unique. - 6If a table is in 2NF what does it consist of?- all its non key attributes are dependant on the entire primary key.
- based on functional dependance. - 7If a table i sin 3NF what does it consist of?- no functional dependancy
- it is in 2NF - 8Advantages of normalisation.- removes redundancy
- increases consistency
- increases integrity
-easier maintenance
-flexibility for future expansion - 9Disadvantages of normalisation.-reduced database performance
-takes a longer time
-some require a lot of inserting, editing and deleting of data
-some need to break the rules of normalisation - 10Whats the difference between a simple query and a complex query?a complex query is a parameter query that searches using more than one parameter value.
a simple query uses only one parameter. - 11Whats the difference between a static and dynamic query?a static query is hard coded into the query and cannot be changed by the end user.
a dynamic query gives a request for the parameter given to the end user at run time. (are able to change it at the end)
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- FlashCards sobre Chapter 5, criado por greek010 em 16-04-2013.
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