Ch.11.3 Using Databases_sc

Foreign Key

A primary key from one table that is used in another table.

Is one table in a database enough to enter all my information in it and store all the fields?

No, you need to create different tables and categorize data to be stored in them.

Creating Database Tables. When you create a database, you must organize data into various tables based on logical groupings. Each table in the database should contain a related group of data on a single topic. For example, at a college you might find a number of different tables in a database:

1. A table that includes student contact information names, addresses, and so on) 2. A table that includes course information (names of courses, credits per course, and so on) 3. A table that includes financial aid information (types of financial aid, amount paid, and so on) When tables are created properly, the goal is to reduce data redundancy by recording data only once. This process is called normalization of the data.

data type -field type

1. Describes the kind of data being stored at the memory location; each programming language has its own data types (although there is some degree of overlap. 2. In a database, indicates what type of data can be stored in a field and prevents the wrong type of data from being entered into the field.

Types of Databases. There are three main types of databases: type 1

1. Relational databases include only data, which is organized into separate logical groupings (or tables) that contain related data. For example, at a college, a database could have a table with student contact information and another table with class registration information.

Data Types. When you create a database, you assign each field in the database a field name. You also indicate what type of data can be stored in the field. This is called the data type (or field type). The following are common data types in Microsoft Excel:

1. Short Text fields store text and/or numbers. 2. Number fields store values that can be used to perform calculations. 3. Calculated fields store the contents of a calculation. 4. Date/Time fields store dates and times. 5. Long Text fields store long pieces of text. 6. OLE Object fields store objects like pictures or video clips. 7. Hyperlink fields store hyperlinks.

type 2

2. Object-oriented databases store data in objects, not tables. These objects contain not only data, but also methods for processing or manipulating that data. Object-oriented database are adept at handling unstructured data such as audio and video clips, pictures, and extremely large documents.

type 3

3. Multidimensional databases store data in multiple dimensions. This distinguishes them from a relational database, which stores data in two-dimensional tables. Multidimensional databases organize data in a cube format.

Advantages of Using Databases. 3 and 4

3. Through a series of validation and consistency checks, databases ensure that the data stored in the database is accurate and reliable. 4. Databases can manage larger amounts of data and can process that data more efficiently than can Excel spreadsheets.

Advantages of Using Databases.

A database is a collection of related data that can be easily stored, organized, and queried. Databases provide many advantages over simple Excel lists. 1. Databases allow you to organize, view, and print the data they contain in a variety of ways to suit individual users' needs. For example, Ron's admissions office can create a report showing total student enrollment, while the financial aid office can create a report showing which students are behind in payments. 2. By centralizing data in one place, databases make it easier for users to share data. And, because users only have to enter data into one place in the database, they reduce the possibility of errors being introduced when data is entered or updated.

hyperlink field

A field that stores a link to a file, e-mail address, or Web site address.

calculated field

A field that stores the value of a mathematical operation.

How do I create fields in a database?

Actually, you can create the fields manually by assigned field names.

How do I get started on creating a database?

Before creating a database, you need to know the three main components of a database. These include fields, records, and tables.

Database Components

Databases have three main data storage components. 1. A category of information in a database is stored in a field. Fields are displayed in columns. Each field is identified by a field name. Here City, State, and Class Code are field names. 2. A group of related fields is called a record. Here, contact details and class registration information constitute one record. 3. A group of related records is called a table (or file). Tables usually are organized by a common subject. This group of related records containing student information constitutes a table.

Foreign Key. In relational databases, "relationships" are established among tables to allow the data in the tables to be shared. In order to establish a relationship between two tables, the primary key of one table is included in the related table. example, a college database would have 1 table with student contact information -name, city, state, phone, and another table with residence assignment -ResidenceID, room number and so on.

For example, a college database would have one table with student contact information (name, city, state, phone, and so on) and another table with residence assignment (ResidenceID, room number and so on). These two tables would be linked by a primary key such as a student ID number. When the primary key of one table is included to establish a relationship with another table, it is called a foreign key in the related table. Foreign keys in related tables have to contain the same type of data as that in the primary key.

Primary Key. To understand how tables work together in databases, you first have to understand primary keys. Each record in a database table is assigned a primary key (or key field) to ensure that the record is unique and won't be confused with other records.

For example, in your student record, a primary key might be your student ID or Social Security number because no other student at your school will have the same number as you do. In this table, two students have the same name. However, the records are never confused with each other because each student is assigned a unique Student ID. The Student ID field is the primary key. By establishing a primary key and ensuring that it is unique, it is not possible to duplicate records in a table.

Short Text field

Hold any combination of alphanumeric data (letters or numbers).

OLE Object field

Holds items such as pictures, video clips, or documents.

Long Text field

Like a text field but can hold long pieces of text.

Number field

Stores values that can be used to perform calculations.

Primary Key

The field selected as a unique identifier for the database.

What are the different types of databases and which is the most common?

There are relational, object-oriented, and multidimensional databases. Of these, the relational database is most common.

But, if I include the primary key of one table in the other table, won't I have two primary keys for a record?

When the primary key of one table is included in another table to establish a relationship between the two tables, it is called a foreign key in the related table.

A category of information in a data is stored in a field. A group of related fields is called a record, and a group of related records is a table.

When you create a database, you must organize data into various tables based on logical groupings. In relational databases, "relationships" are established among tables using primary keys and foreign keys.

What else can I store in a field besides text, numeric values, and contents of a calculation?​

You can store pictures and video clips using OLE Object fields.

What data type can I use for a field if I have to store a page of text?

You can use memo fields. They are text fields that are used to hold long pieces of text.

How do I create relationships between tables?

You use primary and foreign key fields to create relationships between tables.

A database is

a collection of related data that can be easily stored, organized, and queried. Database enable multiple users to share and access data simultaneously. There are three main types of database: Relational databases, object oriented databases, and multidimensional databases