This article is the first of a series on how to retrieve and update information stored in databases. It is organized into the following references:
A database is a collection of information applicable to a particular subject or purpose. The data is typically grouped into specific categories of information, which are contained in data storage files called TABLEs. A database can have multiple tables.
Tables organize data into rows called RECORDS and columns called FIELDS.
A table's structure defines the type of fields needed to contain the desired information. For example, a table's fields can store different data types such as character strings, integers, floating-point numbers, dates, and even images, which are specified at the time a table is created.
You can think of a database table as an advanced type of an index-card file. For example, an employee phone list consists of index cards filed in alphabetical order by the employees' last names. Each card contains an employee's ID number, last name, first name, and company phone extension.
Together, all the cards in the index-card file make up a TABLE. Each employee's card comprises a RECORD, and each item that stores specific information about the employee corresponds to a FIELD. In the employee phone list, for example, the employee's first name is one field; the last name is another field, and so on.
We use these fields to gain access to the information we want in the database. Typically, we use the field name or label that identifies the field ( for example, LastName ), to set or retrieve the value that is stored in the field ( for example, 'Smith' ).
A database can also have multiple VIEWs. A view has records and fields just like a table, but it can contain information from different tables. In some relational database management systems ( RDBMS ), a view is called a query, and it can accept parameters that change the information it displays.
In subsequent articles, we shall take a closer look at how to display information from, and input information to, the records and fields of a database. But first, we need to know how to access the data source.
