Entity is real world thing,person,place,event or object about which store data in database.

Attribute are the characteristics of entity is called attribute.

single value attribute is one that holds a single value for a single entity.

example:- name, roll_number...

multivalued attribute is one that holds multiplevalues for a single entities.

example:- degree(phd, mca)

EAV can stand for: # Equine Arteritis Virus # Entity-Attribute-Value # Erste Allgemeine Verunsicherung

Put /* block comments */ around it, for example:

style {

attribute: value;

attribute: value;

attribute: value;

}

style {

/* attribute: value; */

attribute: value;

attribute: value;

}

or

style {

/* attribute: value;

attribute: value; */

attribute: value;

}

or

/* style {

attribute: value;

attribute: value;

attribute: value;

} */

And while this won't validate, attribute renaming uses a lot less typing (and I use it myself):

style {

xattribute: value;

attribute: value;

attribute: value;

}

Attributes can be classified as identifiers or descriptors. Identifiers, more commonly called keys or key attributes uniquely identify an instance of an entity. If such an attribute doesn't exist naturally, a new attribute is defined for that purpose, for example an ID number or code. A descriptor describes a non-unique characteristic of an entity instance.

An entity usually has an attribute whose values are distinct for each individual entity. This attribute uniquely identifies the individual entity. Such an attribute is called a key attribute. For example, in the Employee entity type, EmpNo is the key attribute since no two employees can have same employee number. Similarly, for Product entity type, ProdId is the key attribute.

There may be a case when one single attribute is not sufficient to identify entities. Then a combination of attributes can solve this purpose. We can form a group of more than one attribute and use this combination as a key attribute. That is known as a composite key attribute. When identifying attributes of entities, identifying key attribute is very important.