Study Set Content:
what is database?
storing large amount of data as a structure
we can save data into?
pc(using memories) and server(for large amount of data)
what is dbms?
dbms is a software like sql it does create and manage database to the server or serveres in the pc
file system drawbacks?
- Data redundancy => waste of memory
- Data Inconsistency => saving files and forgetting which one is the last update one
- Difficulty in accessing data => writing new program to do task like a login page u need other program for user and password but database just ask u entering in one page
- Limited Data Sharing : using files of type psd or others will be problem cus u need a program for each of them
- integrity problems : logic problems and u cant edit exist ones
- update problems: u cant edit or change old data to update but database does
- mutiple user cant use a program at same time
- secuirty problem
abstraction means?
data hiding from user by logical level
absraction levels are?
physical levels --> can see data on the drive physic part
logical levels ---> can see data s a software like a table
view levels -- > only can see the data which leted from logical level to see
means user levels students for example
abstrction views - like physical can see what?
physcal can see both users and logicals data and may can changes
logical can see users data and can change it
view leevel only can see herself or himself data and can change some of them and cant change most of them which logical can do all
how to show data systems by using dbms?
accessed
stored
update
connected
popular data model?
relational model = links between table model
relational database made by who?
when?
edgar f codd 1970 (in case he asked just better to kno everything)
how does relational model works?
it uses tabluar form to store data as field and columns
relatiosnship means?
links between each tables = foreign key and primary key stuff
relation means?
tables
relationship between relations means what?
links between tables
colum --> f..
row --> re..
colume = field
row = records or data
what is relational dbms??
dbms is a softwar managain or retrieve and store data to database
--
relational dbms is a specefic type of software that only works on relational databases means u can manage relational database with this spsecefic softwares which is sql
3 types dbms of relational database?
mysql
oracle
microsoft sql server
how can u show ur database daiagram?
name of table or relation
then name of fields and notice primary key too
what is primary key in database?
a unique data or identifier in every table we have to have one primary key no more no less , like id and passport etc
what is foreign key?
its actually primary key but in another table
to be clear : a table that give primary key is the parent
and a table that retrieve primary key it's the child table and the name of column will be foreign key
