The most recent of these three database models, overcomes some of the limitations of the other two models. The relational model represents all data in the database as simple two dimensional table called relations. The tables appear similar to flat files, but the information in more than one file can easily extracted and combined. Sometimes the tables are referred to as files.
The principal advantage of the hierarchical and network database models is processing efficiency. For instance, a hierarchical model is appropriate for airline reservation transaction processing systems, which must handle millions of structured routine requests watch day for reservation information.Hierarchical and network structures have several disadvantages. All the access paths, directories, and indices must be specified in advance.
They are not easily changed without a more programming effort. Therefore, these designs have low flex flexibility large relational database may be designed to have some data redundancy to make retrieval of data more efficient, the same data element may be stored in multiple tables. Up dating redundant data elements is not automatic in may be relational database management system. The strengths of relational database management system are great flexibility in regard to ad hoc queries, power to combine information from different sources.
The principal advantage of the hierarchical and network database models is processing efficiency. For instance, a hierarchical model is appropriate for airline reservation transaction processing systems, which must handle millions of structured routine requests watch day for reservation information.Hierarchical and network structures have several disadvantages. All the access paths, directories, and indices must be specified in advance.
They are not easily changed without a more programming effort. Therefore, these designs have low flex flexibility large relational database may be designed to have some data redundancy to make retrieval of data more efficient, the same data element may be stored in multiple tables. Up dating redundant data elements is not automatic in may be relational database management system. The strengths of relational database management system are great flexibility in regard to ad hoc queries, power to combine information from different sources.
