Database Management

This paper is based on a case of database query optimization for a local traveling firm, which had hired me as Database Administrator. The firm was responsible to handle the data of all the passengers arriving and departuring from the local airport, situated in London. The firm was finding it difficult to manage the task, due to an ever-increasing number of passengers using the airport. Infact one of the basic problem was that all the data were handled manually and the computer operator had to do the dual job of recording the data in the record file and than on the excel sheet.

When I was hired and given the responsibility to check out the problem, I readily advised the top managemnt of the company to switch its manual data to an Relationsl Database Management System (RDBMS). The shift proved very beneficial as it was efficient and cost-effective: Details of the newly devised query optimization using RDBMS is given below:

Figure 1: Airport Relation Containing Information About International Airports

Querying RDBMS

The structure in the relational model enables an RDBMS to efficiently respond to questions (queries) about the data. Several fundamental query types, called relational operators, are defined in the relational model. All the relational operators take one or more relations as input and return a single relation as output. This discussion will concentrate on just three of the most important relational operators: restrict, project, and join (Worboys, 18).

The restrict operator takes one relation as its input and outputs a relation containing a subset of tuples from the input relation. The restrict operator has the general form “restrictcondition (tablename),” where “tablename” specifies the name of the input relation and “condition” specifies which tuples in the input relation are to be kept in the output relation. For example, the following query could be used to find only those airports located in the Southern Hemisphere (i.e., those with negative latitudes):

Figure 2 shows the relation that is produced by this query. The project operator takes one relation as its input and outputs a relation containing a subset of attributes from the input relation. The project operator complements the restrict operator, selecting attributes rather than tuples. The project operator has the general form “projectattributelist (tablename),” where “tablename” again specifies the name of the input relation and “attributelist” specifies a list of attributes in the input relation that are to be kept in the output relation. For example, the ...