What is E-R diagram[DBMS-4]

-

E-R diagram

-E-R diagram is the entity relationship diagram.
-E-R diagram can express the logical structure of the database graphically.
-E-R diagram can consist of the following major components.


-The entity sets are represented by the rectangular.










-The attribute are represented by the ellipse.











-The relationship are represented by the diamond and rhombus.











-Line is used to link attribute to entity sets and entity sets to relationship sets.




-double ellipse is represented to composite attributes.









-Dotted ellipse is represented to dotted derived attributes.







It is represented to composite attributes.










-Key attributes.






-Double rectangle represented to work of entities.













-Double line indicate to the particularization of an entity set in the relationship sets.






-One to one


-One to many


-Many to one



-Many to may

Comments

Post a Comment

Popular posts from this blog

What is queries in SQL[DBMS-6]

-
Queries in SQL Data types character: -This types of data types store the characters string in fixed length. -The size in brackets determine the no of characters the shell can hold. -character data types is 255 characters. var character(size)/var char 2 (size): -This character is used to store variable length alpha numeric data. -Var char is 2000 character. date: -Date data type is used to represent to the data / time. -The standard. format is dd/mm/yy. Number: -The number data type is used to store number no of any magnitude may be stored up to 38 bit.  
Read more

What is demand paging(OS-9)

-
Image
Demand paging -Loading the entire program in the physical memory at program execution time is not so good because the user does not need the entire program in memory at a time. -An alternative strategy is to load pages only as they are need this technique is known as demand paging. -With demand paging virtual memory, pages are only loaded when they are demanded during program execution pages that are never accessed thus never loaded into physical memory.    -A demand paging system is a similar to paging system with swapping, -But here it uses a lazy swap where it never swap a pages into memory unless that page will be need. -In demand paging pager is more suitable than swap er. 
Read more

Draw process state diagram and explain each state(OS-3)

-
Image
-Process state means current activity of process. -When process is execute it changes the state generally state of process is determine by the current activity of process. -Each process may be in one of the following state. new- the process is being is oriented. ready- the process is waiting to be assigned to the processor. waiting - the process is waiting for some event (I/O operation) to occur. running - the process is being executed.  terminated -the process as finished the execution. process state diagram: -The pictorial is represented to the process changing from one process to another process during       there  execution is known as process state diagram. -A process can be change for one process in the following manner. new ready: The operating system(os) create a process and prepares the process to be executed ,then the os moved the process into the ready queue.  ready running: When it is time to select a process to run, the os selects one jo
Read more