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Database Programming
Databases are collections of tables that maintain and display information, often collaboratively; this information can be used for interaction with an application or gaining general knowledge. Questions about database engines and modifying or using them belong in this category.
8,803 Questions
What is the difference between object based model and record based model?
Object Model: deals with object oriented "blue-print" of your system. This includes, class diagrams (classes you will be creating), relationship between these classes, methods in the classes, properties etc.
Data model: deals with entities at the database level. Like how the classes in the OM will get stored in the database, in which tables etc. So DM deals with Table schema, relationship between different tables (PKs, FKs) etc.
Example:
DM does not have complex OO features like polymorphism, inheritance, overloading etc which are usually listed in an OM.
As a rough example, two classes in the OM can get stored (mapped) to a single Table in the DM, like both Employee and Manager persons can be stored in a single DB table.
What is lack of flexibility of traditional file environment?
A traditional file system can deliver routine scheduled reports after extensive programming efforts, but it cannot deliver ad-hoc reports or respond to unanticipated information requirements in a timely fashion.
What are five strengths of the database approach?
Reduced data redundancy, Improved data integrity, Shared data, Easier access, Reduced development time
What is a subsystem of a DBMS?
A subsystem of a Database Management System (DBMS) refers to a specialized component that performs a specific function within the overall architecture of the DBMS. Common subsystems include the Storage Management subsystem, which handles data storage and retrieval; the Query Processor, which interprets and executes database queries; and the Transaction Management subsystem, which ensures data integrity and consistency during concurrent operations. Each subsystem works together to provide the functionality and reliability expected from a DBMS.
Four ways data can lose its integrity?
1. someone deleting it
2. Virus on system
3. Did not save data
4. corrupt files
What is logical view of database?
The logical constists of the name of the table, the attributes it contains, their types, the constraints on the attributes, if any.
What are the different types of normal forms?
First normal form, second normal form, third normal form, fourth normal form, fifth normal form and Boyce Codd normal form. See the related question below.
What letters or numbers appear on a red cone shaped buoy?
These cone-shaped buoys are always marked with red markings and even numbers. They mark the edge of the channel on your starboard (right) side when entering from the open sea or heading upstream.
A database can perform four core operations, known as CRUD (Create, Read, Update, and Delete). Create is the ability to insert information into the database. Read is the ability to retrieve stored data, possibly transforming it during this process. Update refers to the ability to store newer information in place of older information. Delete refers to the ability to remove data that is no longer needed.
How would you structure a database for tracking a family tree?
Identify the entities in the database
Select the unique identifier/primary key
Identify appropriate attributes
Select the appropriate data types
Create a recursive relationship
Identify the cardinality of a relationship
How would a travel agent use a database?
to keep track of all customers and resort info also flight information
What are one to many and many to many Relationship in database?
Relationships happen between two tables.
One to Many means that one objects (called tuples, or rows) of Table A is related to one or more objects in Table B.
For example, if a doctor can work only in one hospital, and we have a table of hospitals and a table of doctors, Hospitals has a One to Many relationship with Doctors, because for each hospital you will have one or more doctors working at it.
Many to Many means that for each object in Table A, one or more objects in Table B are associated, and viceversa.
In the example, if doctors are allowed to work in different hospitals, the table Hospitals and the table Doctors have a Many to Many relationship.
Now, how to implement this in a relationship DB, that is another question.
To make generalizations about future events based on inferences from data?
Prediction... Foretelling... Extrapolation...
What is the advantages and disadvantages of manual data capture?
Advantages:
- More accurate information: An interviewer is able to get the exact thoughts and feelings of the person being interviewed, instead of just a single answer.
- Can be stored for later use: If a computer saves too much data it will eventually run out of space.
- Lower cost: It may be cheaper to buy writing materials rather than buying computers
Disadvantages:
- It is hard, tiring work: Most people prefer to sit at a computer and type all day rather than to run around interviewing thousands of people in a day.
- Lack of space: It takes less space to save documents on a computer than to file millions of papers.
- Speed: Sometimes it takes a long time to type information into a computer.
What are all the kinds of bytes?
this is in order from samllest to biggest :
Bit = 1bit
Byte = 8bits
Kilobyte (kB) = 1024 bytes or 10^3
Megabyte (MB) = 1048576 bytes or 10^6
Gigabyte (GB) = 1073741824 bytes or 10^9
Terabyte (TB) = 1099511627776 bytes or 10^12
Petabyte (PB) = 10^15 bytes
Exabyte (EB) = 10^18 bytes
Zettabyte (ZB) = 10^21 bytes
yottabyte (YB) = 10^24 bytes
(this is as far as i know)
