BIT: the smallest unit of data a computer can handle.
BYTE: Combination of BITS called a byte, represents a CHARACTER which can be a letter, a number or another symbol.
FIELD: A grouping of characters into a word, a group of words, or a complete number (such as person’s name or age ).
RECORD: A group of related fields, such as the student’s name , the course taken , the date , and the grade comprise a RECORD.
FILE: A collection of similar RECORDS.
DATABASE: A group of related files makes up a DATABASE.
DATABASE ORGANIZATION’S ELECTRONIC LIBRARY STORES & MANAGES DATA IN A CONVENIENT FORM *
Bit Byte Field Record 0, 1 01001010 (Letter J in ASCII) John Stewart (NAME field) John Stewart IS 101 F02 B+ NAME COURSE DATE GRADE File John Stewart IS 101 F02 B+ Karen Taylor IS 101 F02 A Emily Vincent IS 101 F02 C NAME COURSE DATE GRADE Database Course file Financial file Personal history file HIERARCHY Example Student Database
SELECT : lists the columns from tables that the user would like to see in a result table.
FROM : identifies the tables or views from which the columns will be selected.
WHERE : includes conditions for selecting specific rows (records) within a single table and conditions for joining multiple tables.
SQL Part number Part description Unit price 137 145 150 152 Door latch Door handle Door seal Compressor 22.50 26.25 6.00 70.00 Supplier number 4058 2038 1058 1125 Database Supplier number 4058 2038 1125 CBM Inc. Ace Inc. Bryant Corp. Supplier name Supplier address 44 Winslow, Gary, IN 44950 Rte, 101, Essex, NJ 07763 51 Elm, Rochester, NY 11349 PART SUPPLIER
Suppose, you wanted to see the same data only for parts in the PART table with unit prices less than $25.00. You would specify:
SELECT Part_Number, Part_Description, Unit_Price
Part number Part description Unit price 137 150 Door latch Door seal 22.50 6.00 The results of using a conditional selection to select only parts that meet the condition of having unit prices less than $25.
The data are standardized into a common data model and consolidated so that they can be used across the enterprise for management analysis and decision making.
The data are available for anyone to access as needed but cannot be altered.
Much like a physical warehouse for products and components, the data warehouse stores and distributes data on computer-based information systems.
Operational data Historical data Operational data Historical data External data External data INTERNAL DATA SOURCES EXTERNAL DATA SOURCES Extract and transform Data Ware- house Information directory Data Access and analysis
Databases require new software and a new staff specially trained in DBMS’ techniques as well as new data management structures.
Most corporations develop a database design and management group within the corporation that is responsible for defining and organizing the structure and content of the database and maintaining the database.
Network DBMS depict data logically as many-to-many relationships.
More flexible than the hierarchical structure in support of databases for many types of business operations.
A typical many-to-many relationship for a network DBMS is the student-course relationship. There are many courses in the university and many students. A student takes many courses and a course has many students.
NETWORK DATA MODEL MANY-TO-MANY: STUDENT A STUDENT B STUDENT C CLASS 1 CLASS 2
The most popular type of DBMS today for PCs as well as for larger computers and mainframes is the relational DBMS.
It can relate data stored in one table to data in another as long as the two tables share a common data element.
Easier for programmers to work with and easier to maintain than the hierarchical and network models.
Leading mainframe relational database management systems include IBM’s DB2 and Oracle from the Oracle Corporation.
MS Access is a PC relational database management system.
Part number Part description Unit price 137 145 150 152 Door latch Door handle Door seal Compressor 22.50 26.25 6.00 70.00 Supplier number 4058 2038 1058 1125 Supplier number 4058 2038 1125 CBM Inc. Ace Inc. Bryant Supplier name Supplier address 44 Winslow, Gary, IN 44950 Rte, 101, Essex, NJ 07763 51 Elm, Rochester, NY 11349 PART SUPPLIER RELATIONAL DBMS Select Part_number=137 or 152 Join by Supplier_number Part number Supplier number Supplier name Supplier address 137 152 4058 1125 CBM Inc. Bryant 44 Winslow, Gary, IN 44950 51 Elm, Rochester, NY 11349 Combined data from two different tables and only selected attributes are displayed.
Many applications today and in the future will require databases that can store and retrieve not only structured numbers and characters but also drawings, images, photographs, voice, and full-motion video.
Stores data & procedures as objects.
Conventional DBMSs are not well suited to handling graphics-based or multimedia applications.
They are becoming more popular because they can be used to manage the various multimedia components or Java applets used in Web applications which typically integrate pieces of info from a variety of sources.
How data are to be physically stored and accessed on the storage devices
CREATING A DATABASE E ntity-relationship diagram
Database designers document the logical data model with an entity-relationship diagram (ERD) which is a methodology for documenting databases illustrating the relationship between various entities in the database.
ENTITY- RELATIONSHIP DIAGRAM Entities Relationships Entity Attributes M 1 M 1 ORDER CAN HAVE PART SUPPLIER CAN HAVE ORDER: #, DATE, PART #, QUANTITY PART: #, DESCRIPTION, UNIT PRICE, SUPPLIER # SUPPLIER: #, NAME, ADDRESS