An entity is a group or class of things, such as people, objects, and places. They are essentially nouns, things that would be searched for in a structured database or table. An attribute is a feature or description or characteristic of an entity, such as fields. Data items are the actual words or text or numbers in a field of a database’s records or fields. Keys are special parts of fields’ data. These make the data distinct from other records. For example, a key field could be the driver’s license number for a record. But, since a driver’s license might appear multiple times for some reason, another type of field is needed. A primary key field further distinguishes records to make it unique. A primary key field might be a “compound key”, where multiple fields would be designated to make records unique. A relationship is a link or a join between two records so that related information can be found quickly and presented in a structured, useful way.
There are many necessary reasons for using a relational database instead of a non-relational database. Non-relational database is often just a huge collection of data with no specific “link” associating information that could be made useful. A relational database helps by structuring the organization, layout, access, presentation, and security of information. A relational database also removes unnecessary redundancy in the main tables while the detail tables would contain duplicates that are necessary. For example, a database might contain a table that has no duplicate drivers’ license numbers. But, a joined or related table might have multiple records related in another table. The relational link makes related records match up to something being searched. The main table would have non-duplicated drivers’ license numbers, but each time a ticket, crash, or other incident is associated with a driver, that information would be in a detail table, linked to the main table by the driver’s license number.
2. What are 5 characteristics that distinguish relational and non-relational databases? Find an example of where a non-relational database was chosen over a relational one, cite it, and write in your own words and reasoning as to why one was chosen over the other.
Relational databases are designed to remove redundancy as much as possible. They also enable better security and access control to information in the tables. Many relational database management systems meet ACID test requirements. Relational database systems can enforce what kind of data can be entered into the databases. Also, when schemas and ERDs are used, it can be vastly simpler to use a relational database management system to ensure the right types of data are entered into fields.
However, for small amounts of unrelated information, an RDBMS may be overkill. One does not need an RDBMS for keeping track of grandma’s holiday recipes. But, if one is analyzing terabytes of DNA or genome or astronomy or other types of information not following or not provided in structured formats, a non-relational database system may be necessary simply because it may impose fewer constraints. It could be basic SQL language without interfaces intruding. It might be a highly flexible RDBMS that allows the system architect to disable or “loosen up” numerous constraints. http://readwrite.com/2013/03/25/when-nosql-databases-are-good-for-you http://stackoverflow.com/questions/7935281/why-would-i-want-to-use-a-non-relational-database
3. What are three differences between virtualization and parallel (distributed) computing?
Virtualization is presentation of an electronic version of