A relationship with attributes should be an associative entity when:
- All relationships for the associative entity should be many
- The associative entity could have meaning independent of the other entities
- The associative entity should have attribute(s), but it may or may not have an identifier
- The associative entity may participate in other relationships other than the entities of the associated relationship
- Ternary relationships should be converted to associative entities
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An associative entity is used to represent a many-to-many relationship between two or more entities in a database, while a relationship with attribute represents additional information or properties about the relationship itself. In other words, an associative entity helps in resolving many-to-many relationships, while a relationship with attribute adds details about the connections between entities.
A primary key is an attribute (or combination of attributes) that uniquely identifies each row in a relation. A primary key is designated by underlining the attribute name. The primary key of an entity set allows us to distinguish among the various entities of the set. A foreign key is an attribute in a relation of database that serves as the primary key of another relation in the same database.
Metadata is the data that describes information: language, who it is for, the source etc. Attribute data is composed of the attribute name and attribute value for example: "Color=red" where color is the attribute name and red is the attribute value.
Attribute is the property of entity.The composite attribute is like address(where street no,house no,town name all include).Composite key is also an attribute,but only which attribute are work as a unique identifier. Example:> In an ERD if vendor placed with orders then order(order day, order number) vendor(vendor code,vendor address) Here, order and vendor both are entity and order number, vendor code both are Composite key(because those are unique)but vendor address is a Composite attribute and order day(may be not unique)is an attribute only. So, we can conclude that all attribute not Composite key.
Data refers to raw facts and figures, while a data element is a unique unit of data that represents a specific attribute or characteristic. Data elements are used as building blocks to organize and structure data within a database or system.
A primary key uniquely identifies each record in a table and ensures data integrity. A foreign key establishes a relationship between two tables, referencing the primary key of another table to enforce referential integrity.