The purpose of a database is to keep track of things. Spread sheets are also used quite frequently to track information in organizations.
Q2: What is a Database?
A database is a self described collection of integrated records. A byte is a collection of data. Bytes are grouped in to columns. Columns are also fields. Columns and fields are grouped into rows which are also called records. Rows and records are grouped into a table or a file. A key is a column or group of columns that identify a unique row in a table. Relational databases are databases that carry their data in the form of tables and that represent relationships using foreign keys. Metadata are data that describes data.
Q3: What Is a Database Management System (DBMS)?
A database management system is a program used to create, process, and administer a database. Companies license DBMS products from vendors such as IBM, Microsoft, Oracle, and others. Popular DBMS products are DB2, Access and SQL Server, and Oracle Database. Another popular DBMS is MySQL. DBMS and a database are two very different things. A DBMS is a software program; a database is a collection of tables, relationships, and metadata. Database developers use the DBMS to create tables, relationships, and other structures in the database. The second function of the DBMS is to process the database. A third DMBS function is to provide tools to assist in the administration of the database. Database administration involves a wide variety of activities.
Q4: How do Database Applications Make Databases More Useful?
A database application is a collection of forms, reports, queries, and application programs that process databases. Data entry forms are used to read, insert, modify and delete data. Reports show data in a structured context. Multi user processing can have issues such as the lost update problem mentioned in the book about two people trying to sign up for one vacant spot. Enterprise DBMS are used for large organizational and workgroup databases. Personal DBMS are designed for smaller, simpler database applications.
Q5: How Are Data Models Used for Database Development?
Data models describe the data and relationships that will be stored in the database. It is just a blueprint for the database. Database Development Process is Forms/Reports/Queries à Create data model à Create database design à create database. Entity relationship (E-R) data model is a tool for constructing data models. It is used to describe the content of a data model by defining the things that will be stored in the database and the relationships among those entities. Unified Modeling Language is another tool. Entity is something that users want to track. They are always singular and some represent physical object. Entities have attributes that describe characteristics of the entity. (example: OrderDate, Tax, Total). An identifier, which is an attribute or group of attributes, whose value is associated with 1 and only 1 entity. Entities have relationships with other entities. An entity-relationship diagram is used by database designers. Crows feet ( --< ) are used to link one to many relationships (example teacher to students). Many to many relationships is where one advisor can have many students and one student can have many advisors. Maximum cardinality is the maximum number of entities that can be involved in a relationship. Examples are 1:N, N:M, 1:1. Minimum cardinalities is the min amount of entities.
Q6: How is a Data Model Transformed into a Database Design?
Normalization is the process of converting 1 poorly structured car into 2 or more well structured tables. Data Integrity Problems is where information is not correct across the tables. (accounting/financing example in book). General goal of normalization is to construct a table such that every table has a single topic or theme.
Q7: What is the Users’ Role in the Development of Databases?
User review of the data model is crucial. Once a database has been created, it can be very expensive to change to a more optimal model. Entities must contain all of the data you and your employees need to do your jobs and relationships must accurately reflect your view if the business.
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