Database Administration System Set 7
A candidate key is a straightforward or composite key that is distinctive and minimal. It is exclusive as a outcome of no two rows in a table may have the same value at any time. It is minimal as a result of every column is important in order to attain uniqueness. Derived attributesare attributes that comprise values calculated from different attributes. An example of this can be seen in Figure eight.5. Age could be derived from the attribute Birthdate.
The extended entity relationship model is typically known as the ____. All the opposite attributes apart from the important thing attribute are the non-key attributes. Two or extra entities can have the same worth for this attribute. For example, the Class attribute would have the identical value for all these students who are learning in the same class. The value of this attribute is derived from another attributes. We know the value of another attributeand from stored attribute, we are deriving the worth of this attribute.
If an entity can exist other than a number of related entities, it’s said to be ____-independent. A ____ may be represented with a single-valued attribute. A derived attribute is indicated in the Chen model by a ____. A ____ attribute could be further subdivided to yield extra attributes. All the content obtainable on this blog is for informational functions only.
The RRE Trucking Company database includes the three tables in Figure 8.12. Use Figure 8.12 to reply questions four.1 to four.5. The primary key of the model new relation is a mix of the first keys of the taking part entities that hold the N side. The linking desk incorporates a quantity of occurrences of the international key values.
Relationships are represented by diamond-shaped field. Name of the relationship is written inside the diamond-box. All the entities collaborating in a relationship, are related to it by a line.
A ____ identifier is composed of more than one attribute. The ____ attribute controls the amount of house inserted between desk cells. Any attribute that’s part of a key is identified why do purely competitive markets tend to benefit consumers over producers? as a ____. An attribute that might be damaged down into smaller parts known as a ________ attribute. A ____ attribute is one that can not be subdivided.
Reproduction and republishing of any contents from here to some other web sites or blogs is strictly prohibited. Knowing the ____ variety of entity occurrences could be very useful at the software software program level. What is a rule that applies to the two-phase locking protocol? Two transactions can not have conflicting locks.
A Student can have more than one Address i.e Permanent Address and Temporary Address. So, it can be known as a multivalued attribute. Without a corresponding employee record, the partner report wouldn’t exist. The entity relationship knowledge model has existed for over 35 years.
Which of the next statements is/are TRUE? Weak entity has at all times whole participation within the identifying relationship. Every relation schema will must have at least one weak entity.
It is represented by a double oval. Some Composite keys can additionally be a multivalued attribute. For instance, the tackle attribute of a pupil can additional be divided into ‘Locality’, ‘Town’ and ‘PIN’. So, we call it a composite attribute. Also, the tackle of a student can have a couple of value.