The Model of Relational Database

by Kh Atiar Rahman - Date: 2008-10-26 - Word Count: 652 Share This!

It is worth mentioning that in the rear, the prologue of SQL s the standard data base as well as the major part of popular data storage space model is the relational database, which was promulgated on a seminal paper named "A Relational Model of Data for Large Shared Data Banks," written by Dr. E. F. Codd in 1970. SQL steps to the fore to tune-up on the outset of the relational database pioneer by Dr. Codd who had disseminated such new discovery for creating and building object orient programming software to be based on the 13 rules, referred to as Codd's 12 Rules, for the relational model which are the basic milestone in RDBMS concept.:  The following rules have been explored by Dr. Codd which are basically known as ‘Dr. Codd's Database rules.

All in progression in a relational database in respect rows and column according to table names is representing explicitly as values in tables. Every value in a relational database is guaranteed to be accessible by using a permutation of the table name, primary key value, and column name. The DBMS provides logical support for the treatment of null values, distinct from default values, and independent of any domain. The portrayal of the database and its contents is represented at the logical level as tables and can therefore be queried using the database language. At least one supported language must have a well-defined syntax and be comprehensive. It must support data definition, manipulation, integrity rules, authorization, and transactions. All views that are theoretically updatable can be updated through the system. The DBMS supports not only set-level retrievals but also set-level inserts, updates, and deletes. Application programs and ad hoc programs are logically impermeable when physical access methods or storage structures are altered. Application programs and ad hoc programs are logically unaffected, to the extent potential, when changes are made to the table structures. Dr Codd has introduced and promulgated the database languages which need to be capable of crucial integrity rules. They must be stockpiled in the online catalog, and they cannot be bypassed. Application programs and ad hoc requests are logically unaffected when data is first strewn or when it is transfer.  It ought not to be prospective to get around the integrity rules defined through the database language by using lower-level languages.

A good number database has had a "parent-child" relationship; that is, a parent node would contain file pointers to its children. This method has several advantages and many disadvantages. In its favor is the fact that the physical structure of data on a disk becomes unimportant. The programmer simply stores pointers to the next location, so data can be accessed in this manner. Also, data can be added and deleted easily. However, different groups of information could not be easily joined to form new information. The format of the data on the disk could not be arbitrarily changed after the database was created. Doing so would require the creation of a new database structure. Codd's idea for an RDBMS uses the mathematical concepts of relational algebra to break down data into sets and related common subsets. For the reason that information can naturally be grouped into distinct sets, Dr. Codd organized his database system around this concept. Under the relational model, data is separated into sets that resemble a table structure. This table structure consists of individual data elements called columns or fields. A single set of a group of fields is known as a record or row. For instance, to create a relational database consisting of employee data, you might start with a table called EMPLOYEE that contains the following pieces of information: Name, Age, and Occupation. These three pieces of data make up the fields in the Job holder table.

Job holder table.






Electrical engineer



Museum curator



Assistant Chef





Related Tags: programming, storage, milestone, object, relational, accessible

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