Hierarchical Database Models Research Paper Example | Topics and Well Written Essays - 750 words

Hierarchical Database Models - Research Paper Example Along with this the data related to the children of an employee would be considered as child data segment. These segments would be linked with the employee record on the basis of 1:n mapping. Further collective instances of records are like tables in relational model. This arrangement contains parent records or nodes which further linked with children data segments, row wise. The popularity of hierarchical databases was established in late 1960s. Network Database Model In the network database model it is allowed to create parent-child relationship on many to many basis. This model follows the organization of graph in which there can be multiple interconnection of a node with other nodes. A conference named CODASYL (Conference on Data Systems Language) was held in 1971 to formally state the properties of network database model. This data model gained a side by side popularity along with the hierarchical model almost. The concept of set is the basic construct in this model. A set compr ises of three components namely, owner type record, name and member type record. A member type record is allowed to be associated with multiple sets. This enables the implementation of more the concept of more than one parents. In this database model the network of records’ relationships is indicated through pairwise sets. Relational Model The relational database model is the basis of Relational Database Management System (RDBMS). The theory and concept of relational model was given by a statistician named E.F. Codd. At the core of the relational model lies the process of normalization. There are more than 5 levels of normalization but usually a 3 levels normalized database is considered as a relational database. The basic procedure comprises of the following steps: Gathering related data in a tabular manner as a flat file. Each row has to represent a unique record. Identification of separate columns and fields to manage data properly. Splitting the flat file into multiple ta bles in order to curb redundancy. Establishment of relationship by declaring and link primary and foreign keys. Enforcement of referential integrity constraints is the part of relationship establishment. There are certain properties of Relational Database Tables which are as follows, Atomic values (the values listed under a single field cannot be decomposed further) Unique records (The data in a rows represents a unique instance of an entity and duplication is not allowed). Homogenous field data (The type of data listed under a field is always same). The columns can be arranged in any manner. Same rule goes with the rows. The results of queries do not get effected due to the any sequential arrangements of either columns or rows. The label of each field is always unique. This assures correct referral of fields in queries. Fields can be set as keys to identify records uniquely. A key may also be composed of more than one field. There are three types of relationships namely One to One, One to Many and Many to Many. The Many to Many relationship is implemented via two decomposed One to many relationships with an intermediate joining table. One to Many relationships are usually represented through the association of two related tables connected in a Master/Transaction fashion. Collective and comprehensive results can be acquired against the queries performed on joined tables (multiple connected tables). The key in a table (Master table) is referred to as