Indexes Are Used From E Commerce Websites - 1481 Words

Answer 1 Indexes are used by queries to find data quickly. Indexes are used to boost performance in a database. Finding an individual record or set of records most efficiently done by Index. Index key is the reference point where an index is an ordered arrangement of keys and pointers. Each key is appointed to the location of the data recognized by the key. For example: when we order any product from E-commerce websites like amazon, we will be assigned an order confirmation ID which gives the authority to track that particular information on the product till it reaches. If no index exists on a table, a table scan must be performed for each table referenced in a database query. The larger the table, the longer a table scan takes because a†¦show more content†¦Ã¯â€š § The primary key attribute cannot be discretionary which means it should not possess null values. ï‚ § The primary key cannot have repeating values which means the attribute may not have more than one value at a time for a given entity case is prohibited. This is known as the No Repeat Rule. ï‚ § Entities with compound primary keys cannot be split into multiple entities with simpler primary keys. This is called the Smallest Key Rule. As we know that a foreign key is an attribute that completes a relationship by identifying the parent entity. Let me explain how to identify the foreign keys that every dependent and subtype entity in the model must have a foreign key for each relationship in which it participates. Foreign keys are formed in dependent and subtype entities by migrating the entire primary key from the parent entity. If the primary key is composite, it may not be split. Foreign key attributes are not considered to be owned by the entities to which they migrate, because they are reflections of attributes in the parent entities. Thus, each attribute in an entity is either owned by that entity or belongs to a foreign key in that entity. If the primary key of a child entity contains all the attributes in a foreign key, the child entity is said to be identifier dependent on the parent entity, and the relationship is called an identifying relationship. If any attributes in a foreign key do not belong to the child s primary key,