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9A Data Design (DBMS components (DBMS provide interface for
User, DBA,…
9A Data Design
DBMS components
DBMS provide interface for
User, DBA, and Related system
User use Query Lanquage to access stored data
- Query Language allow a user to specify a task without specifying how the task will be accomplished
- With a Query by example language (QBE), user provide an example of the data requested
- Structured Query Language (SQL): allow client workstation to communicate with server and mainframe computer
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Related system
- A DBMS can support several related info system
- No human intervention is required for 2-way communication
Data Manipulation Laguage (DML) :red_flag:
A DML control database operations, including storing, retrieving, updating and deleting data
Schema
- is the complete definition of a database, including description of all fields, tables and relationships
- Can define one or more subschema, which is a view of the database used by one or more systems or users
VD: subschema của P management system would not include the pay rate field to protect individual privacy
Physical Data Repository
- Data Dictionary is transformed into a physical data repository
- The PDR might be centralized, or distributed at several location
- Open Database Connectivity (ODBC) allow software from different vendors to interact and exchange data
- Java Database Connectivity (JDBC) enable Java application to exchange data with any database
Data Design concept
Data Structure: consist of files or tables that interact in various ways. Each file or table contain data about ppl, place, thing or event
File-Oriented system (File Processing system)
- Manage data in separate
- Can be cost-effective for simple process
- Potential problem: data redundancy, data integrity
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Data design Terminology
Definition
Entity: is a person, place, thing, event for which data is collected
vd customer, order, product
Table or File: contain a set of related records that store data about a specific entity
vd if company has 1000 customers, the customer will include 1000 records
Field: is a single characteristic of an entity
vd Customer include Name, Address, Email
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Key Fields: used to organize, access,
and maintain data structures
Primary Key: is a field or combi field that uniquely and minimally identify a specific record.
vd Customer ID is a unique primary key
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Foreign key: is a field or combi field that must match a primary key value in another table
vd Advisor number is a foreign key in Student table
Referential Integrity: is a validity check, mean that a Foreign key value cannot be entered in one table unless it match an existing primary key in another table
- Orphan: an order has no related customer
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