databases

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relational database
allows the user to specify information about multiple tables and the relationship between those tables. A database structured to recognise the relationships of the items stored
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flat file database
one big table that stores all the records and atributes, only allows the user to specify data in one record and atribute at a time, stored independently
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primary key
a key that uniquely identifies all thhe reccords in a table
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foreign key
a key that is the primary key in another table with a relation ship to the current table
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concatonated primary key
when one fireld is combined with another to form a unique primary key, like combining peoples names
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secondary key
a key for faster indexing, faster access times
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ERM
entity relationship modelling, the process of abstractly modelling the relationships between tables in a relationa data base
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normalisation
the process of arranging data in tables in a standard way, this involves making new tables and forming relationships between them with keys.
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indexing
the process of creating a database index, a data structure that improves the speed at which data can be accessed, at the cost of taking up more space
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0NF
zero normal form, a flat file with duplicated data`
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1NF requirements
1. eliminate any duplicate attributes 2. separate out records where one of their atributes conatins more than one value 3. identify a primary key / make one / concatenate 4. separate any non "atomic" attributes, like "Adam West, ADWE" would separate
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2NF requirements
1. check in 1NF 2. remove partial dependencies (only if concatenated), if so split the table with that attribut as primary. 3. fix many to many relationships 4. make linking tables if needed
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3NF requirements
1. check in 2NF . check there are no non key dependancies "all atributes are dependant on the key, the whole key and nothing but the key"
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what is SQL
structured query language, the language and syntax to read from databases
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referential integrity
a measure of consistency of data in a database. violated when a foreign key no longer is foreign to anything
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transaction prosessing
information processing that is divided into individual and indivisable operations called transactions. each one is done in ACID
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ACID
atomicity, consistency, isolation, durability
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atomicity
entirely done or not done at all, if a record is being removed so must all its attributes at the same time, or not at all
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consistency
any change to the database must retain the overall state of the database
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isolation
each transaction is done on its own and entirely, two transactions therefore cannot affect eachother. records being changes are locked, once changed it is unlocked
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durability
once a change to a database has been made it must not be lost due to errors, power loss or failure. immediatly written to main memory
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DBMS must be able to
CRUD, create (INSERT/CREATE) Read (SELECT), Update (UPDATE), Delete (DELETE)
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Other cards in this set

Card 2

Front

flat file database

Back

one big table that stores all the records and atributes, only allows the user to specify data in one record and atribute at a time, stored independently

Card 3

Front

primary key

Back

Preview of the front of card 3

Card 4

Front

foreign key

Back

Preview of the front of card 4

Card 5

Front

concatonated primary key

Back

Preview of the front of card 5
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