Database software enables users to create new files; add, delete, or change entries in files; perform limited calculations using data; sort records according to varying criteria; and merge two or more files into one.

To create, test, and manage a successful database, it is necessary to have a thorough understanding of the data to be stored, the reason for their existence, and how they can be managed to provide the desired end product. Based on the type of information to be stored, three types of database structures are available: hierarchical, network, and relational.

Hierarchical Databases. The simplest database is the hierarchical, or tree-structured, model in which information is accessed  from  the top down.  For example,  a social  security  number  may be used  to identify a record followed by a student’s name and address. If the user wants to search the records  and knows only a student’s name, the system must follow the hierarchical path. This method is said to be a parent–child  relationship;  that  is, each  item  relates  only  to the one above  and below it in the hierarchy.

Network Databases. Network databases allow multiple, explicit relationships to exist, rather than only top-to-bottom relationships. The network model also uses a less rigid search structure. The shortest distance to the required information is followed, rather than a top-to-bottom route. The complexity of this system makes modification a more involved procedure.

This model works well for standardized operations wherein transactions predictably follow a preconceived path for each occurrence, such as banking transactions, airline reservations systems, and inventory control.

Relational Databases. A relational model allows multiple associations among common fields in more than one database. Relational databases are arranged in table format, two-dimensionally, with rows and columns. What was referred to in the previous two models as a file is now a relation. A record is now termed a row; a field is now a column. In order to avoid confusion, we will continue to refer to files, records, and fields throughout this description. The relational database performs three basic functions:

Joining. Two files are merged into one.

Projection. Fields are extracted from various files to form a new file.

Selection. Various records may be chosen according to the user’s own criteria; this is called  selection.

Edit. The Edit command is used to change or modify data that are already part of a file. The system displays the entire record and fields can be altered as necessary. Entered changes replace the earlier entries.

Enter. When the user chooses the Enter command, a new record is created and stored in the file.

Field. A field is a category of information. Multiple fields make up a single record.

File. A group of related records is called a  file.

Form. Forms can be created to assist entry and viewing of data. Forms contain input areas based on the database fields.

Query. Running a query allows the user to select only certain records within a file based on a set of criteria. For example, a principal may want to generate a mailing list of parents of a specified segment of the student population; however, the database files contain addresses of parents of all the students. A query can be used to search for only the specified parents.

Record. A record is the basic unit of database organization. The information for each person in a contact database, for example, would be a separate record.

Report. Once a query has been run, the selected data can be displayed and printed in a formatted report.

Sort. The user can reorder records by performing a sort based on any one field of a record. For example, student records might be arranged alphabetically according to students’ names or numerically according to zip codes for mailing purposes. Sorting can be done in ascending or descending order according to the chosen  field.

1. Have students collect information from other students in the school about their physical characteristics (e.g., eye color, height). Design a database in which each type of char- acteristic is a field. Students can manipulate the data to draw some conclusions about   the makeup of the   school.
2. Students can conduct a neighborhood study and record information about the types of businesses and other attractions around the school.
3. Catalog all of the classroom books on a classroom library database. Work with students to devise an appropriate checkout system that they think will work.
4. Keep track of facts learned about a topic studied. Have all students contribute to the fact bank, and generate reports to answer questions about the data.
5. Compare student experiences with search engines. Challenge students to think through what database operations happen when they search for information on an Internet search engine.