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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
A logical database is the structure of data. It is the different pieces of information and the relationships between them.
A data capture form is a document including relevant data boxes to put in a database.
An entity occurrence is essentially an instance of an entity. A great example of an entity occurrence is someone's birthdate and other personal records.
How functional dependency is related to database table design?
The functional dependency is related to the database table design through the foreign and primary keys. The foreign and primary keys are functionally dependent on each other.
OOP stands for object oriented programming. Some characteristics of it include emphasis on data rather than procedure, programs are divided into entities known as objects, and data Structures are designed such that they characterize objects.
What is the difference between char and varchar data types?
The CHAR datatype uses a fixed length, where as the VARCHAR datatype can be variable in length up to the maximum value specified for the length.
If you insert "Hello" into a CHAR(10) field, the column would actually contain "Hello " with 5 trailing spaces.
The same value inserted in a VARCHAR(10) field would contain "Hello".
char datatype is fixed length data type and it store maximum 255 characters while varchardatatype store up to 4000 character of variable length datatype
What are the advantages and disadvantages of disaster management?
In the context of project management it all comes down to risk management - what might happen, what are the chances of it happening, if it happens, what is the result, if it does happen, what can we do about it and how do we stay on top of it. Look at what is highly likely and has the biggest impact on the business/project first and then work down the list until an acceptable level is reached. You can't possibly mitigate everything.
You could look at the following link to get more details and links to other areas: http://en.wikipedia.org/wiki/Disaster_recovery_plan
Some of the advantages of disaster management:
- You can start by developing a disaster recovery / business continuity plan - this will help identify areas of concern. You could engagement with a large community to help you - arrange brainstorming events, interviews, workshops, prepare checklists, questionnaires, get expert facilitation, use data from previous projects, review assumption lists etc. The act of doing this will help you assess each event on a probability scale (1 being highly unlikely to 5 being highly likely).
- Effort can be concentrated on the top 10 events/issue, or the events which have the more importance to the project, the greatest size/value, the most complex or those with a stability/novelty or unknown element.
- Contingency or fallback plans can be developed for the top 10 events or to cover the majority of events.
- Having a plan can help influence the future procurement of new capabilities and services, and even help to dictate where they should be located in order to improve the disaster management in future.
- Issues/events can have owners responsible for ensuring processes are implemented, people are trained, and regular update reports on progress are provided to senior management.
- Future budgets can be set for future improvements.
- It improves corporate knowledge and experience and can prompt people to think laterally and look for alternative solutions, if reviewed regularly.
- Doing something is always better than doing nothing.
Some of the disadvantages of disaster management:
- It can cost a lot of money to develop and implement.
- It can take a lot of effort to do it properly, away from the projects themselves.
- It is not worth doing if it is not done properly.
- It can money to keep it current and update the systems periodically.
Disaster Management is a bit like an Insurance Policy, if you never need it, you wonder why you bought it. But, if you ever do need it, you are ever so glad you did.
What could you use a database for?
A database is used to collect data that is related to each other. For example, a database would be necessary if someone's email contact list held more than 100 names and email addresses.
A foreign key is a primary key or candidate key in the referenced table, it could consists of one or many columns. The foreign key is added to the referencing table. When the foreign keys between the tables are established, the referential integrity relationship
in database system is hence maintained.
While establishing foreign key in the referencing table, we may impose constraints on the foreign key, the constraint will affect how the referencing table's row behaved when it was updated or deleted in the referenced table or vice versa.
There are several constraints, i.e. CASCADE, RESTRICT, SET DEFAULT, SET NULL, NO ACTION.
Here is the example,
CASCADE - Whenever rows in the master (referenced) table are deleted, the respective rows of the child (referencing) table with a matching foreign key column will get deleted as well. A foreign key with a cascade delete means that if a record in the parent table is deleted, then the corresponding records in the child table will automatically be deleted. This is called a cascade delete.
RESTRICT - A row in the referenced table cannot be updated or deleted if dependent rows still exist. In that case, no data change is even attempted. Should not be allowed.
Before setting up a database the data must be collected. This can be done using a data capture form.
The DVD has a greater density. The laser can read finer grooves.
The congress made laws true or false?
True. The Constitution gives Congress the authority to 'make all laws which shall be necessary and proper.'
What data should not be stored in a file?
Passwords, Pin numbers, Social Security Number, any information that is of a personal nature and that can be used to access your most personal data should not be kept in a file. This could lead to identity theft, and/or financial ruining. Protect that which is scared to you.
Extraneous data is that which is not relevant to the specific question or area being considered/analysed.
So, for example, let us imagine you had collected data on all the boys and girls in your class at school. Now let us suppose that you wished to analyse all the data on the boys only.
As you are now only interested in the data relating to the boys, then the data relating to the girls is extraneous for this purpose.
What are some jobs that involve numbers?
Jobs that involve numbers include pharmacists, construction workers, and math teachers. Scientists, and people who reconstruct accidents also have jobs that involve the use of numbers.
What is the difference between schema and database?
Database schema are the logical structure of entities (tables or object classes) and their relationships (keys, or object associations) in a database. Schema can exist at different levels of abstraction (see: en.wikipedia.org/wiki/Database_schema). Schema themselves may or may not exist as such in a database. In general schema at the higher levels of abstraction are design models that are captured in printed documents, and authored by business analysts and database designers, rather than created by database programmers and stored in the database itself. But in some types of databases, schema at any level of abstaction can be realized physically. In Oracle databases, schema can be realized as schema objects, which are a part of an Oracle database. These schema objects may represent a human user's conceptual model of the knowledge captured in an enterprise database. Thus defined, there can be many schema that can be associated with one physical database. In other kinds of relational database, an abstract user's schema can be represented by logically linked metadata, views, and stored procedures assocated with a user class. In object-oriented databases, especially those based on the highly self-referential language Smalltalk (e.g. Gemstone/S), schema are realized as "physical" objects in the database as a matter of course, as well as in the logical models captured in design documents. The schema objects in such databases are, in essence, the classes comprising the infrastructure of the database or application. Oracle-style user schema are readily created; these would be realized as user interface orchestrator classes.
An algorithm can not be written with the following infix expression without knowing what the expression is. Once this information is included a person will be able to know how to write the algorithm.
What is functional dependency in DBMS?
A key is a set of attributes that uniquely identifies an entire tuple, a function dependency allow us to express constraints that uniquely identify the values of certain attribute.
Different from a connectionless protocol, a connection-oriented protocol guaranties the delivery of the information. An example of connection-oriented protocol is (TCP) and a connectionless protocol is (UDP). TCP is a connection-oriented protocol, it makes a connection and checks whether the data is received, and resends if it is not. UDP is a connectionless protocol, it does not guarantee delivery by first connecting and checking whether data is received.
Full meaning of the acronyms dml and ddl state difference within the two?
Details is discussed on http://arjudba.blogspot.com/2008/04/what-are-difference-between-ddl-dml-and.html
What is the importance of data modeling?
A data model is a (relatively) simple abstraction of a complex real-world data environment. Database designers use data models to communicate with applications programmers and end users. The basic data-modeling components are entities, attributes, relationships, and constraints. Business rules are used to identify and define the basic modeling components within a specific real-world environment.
