ch7 Flashcards
what is data modeling
is formal way of representing data that are used and created by a business
what is the one of the most common data modeling technique used in the industry
entity relationship diagramming
(ERD)stand for
entity relationship diagram
what is entity relationship diagram
is picture which shows the information that is created stored and used by business system
what is the meaning of crow foot that closest to the chemical request
that an lca may make many chemical requast
what is the meaning of the two bars closest to the lca
that the chemical request is made by exactly one lca
what is the elemants of entity relationship diagram
entities
attributes
relationships
what is entity in ERD
IS the building block for a data model
it is person place event or thing about which data is collected described in capital letters
what should entities have
name
short dicribtion
what is attribute
is some type of information that is captured about an entity
mcq
attribute is descibed as
noun or verb
noun
the attribute that serve as identifier are noted by ……….next to the attribute name
asterisk
if we put the two attribute the same
what we should do
do concatenation +to be different from the other
we can find a field that make it different from the other
we can generate random number for it
what is relationship in erd ?
are associtions between entities and they are shown by lines that connect the entities together
what is the type of relationship
parent
child
what is parent
the first entity in the relationship
what is the child
the second entity in the relationship
what is the attribute of relationship
should be active verbs
the top words read from parent to child
the bottom words read from child to parent
what is the two prosperities of relationships?
cardinality
modality
what is the cardinality
which is the ratio of parent instance to child instances
what is the meaning of 1:1
relationship means that one instance of the parent entity is associated with on instance of child entity
bar near of the child entity and bar near to parent entity
what is the meaning 1:N
one to many one parent entity to many child entity
what is the meaning of M:N
many to many
what is modality
which refers to whether or not an instance of child entity if the child entity can exist without parent entity
null or not null
page 198
what is null meaning in the erd and not null
null that chemical can exist without
the chemical request
and not null that cannot be chemical request without chemical
what is data dictionary
is in case tool is where the analyst goes to define or look up information about the entities attributes and relationships
what is metadata
the information you see in the data dictionary
is anything that describes an entity attribute or relationship
