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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
How do you delete alternate rows in sql?
delete from table_name where(rowid,0) in (select rowid,mod(rownum,2) from table_name) this is for alternate deleting even row
delete from table_name where (rowid,1)in(select rowid,mod(rownum,2)from table_name)this is for alternate deleting odd row
A database is only limited by the media used to store it ! for example the capacity of a hard-disk.
Flawed data refers to information that is inaccurate, incomplete, inconsistent, or biased, which can lead to incorrect conclusions or decisions. Common sources of flawed data include human error, outdated information, and poor data collection methods. The presence of flawed data can undermine research findings, analytics, and decision-making processes, highlighting the importance of data validation and quality assurance. Ensuring data integrity is essential for reliable outcomes in any analysis or application.
What are the benefits of relational data model?
- structural independence
- simplicity
- ad-hoc query capability
- easy to design
- security control
- non procedural access language
What is the difference between drop and truncate in dbms?
even though both these commands are related to the structure of the table...,we can regain the data when we use use drop command by use of rollback command but its not possible in the case of truncate command.
How do you create table in sql?
create table "table-name" -> exclude the quotes when creating the table
after this a message will come : table created
(row_name data type(limit of characters),... )
for example
(name varchar2(20)).
This will make a column(attribute) in your table with the name "name" and data type varchar with character limit of 20.
you can further add more attributes in the same manner.
to insert values in the table you need this:
insert into "table name" values(123,qwew,wsd,2342)
the data in the brackets above depends on the attributes of your table.
and now you have created a simple table.
you can update, delete, alter, drop the table.
What is data where housing and mining?
it's data warehouse....
data warehouse: it is a collection of multiple databases or it it is repository of data.
data mining it is the process of extracting data from data warehouse.
How do you find maximum in SQL without using MAX function?
Using a left join of:
SELECT a.number FROM table a, table b WHERE a.number < b.number
where right table.number is null
Specifies a key that that is only partially unique. Used for weak entities.
What is the purpose of data model?
The purpose of data modeling
is the formalization and documentation of existing processes and events that occur during application software design and development. Data modeling techniques and tools capture and translate complex system designs into easily understood representations of the data flows and processes, creating a blueprint for construction and/or re-engineering.
What is merging operation in data structure?
Merging is combining the records in two different file into a single file.
How is a concatenated primary key created?
In the table design view of SQL Server, select all the columns that make up the primary key and then select "Set as Primary Key".
Explain the 3 level of Architecture of DBMS?
EXTERNAL LEVEL (highest level)
• The user's view of the database.
• Consists of a number of different external views of the DB.
• Describes part of the DB for particular group of users.
• Provides a powerful and flexible security mechanism by
hiding parts of the DB from certain users. The user is not
aware of the existence of any attributes that are missing
from the view.
• It permits users to access data in a way that is customized to
their needs, so that the same data can be seen by different
users in different ways, at the same time.
CONCEPTUAL LEVEL
• The logical structure of the entire database as seen by DBA.
• What data is stored in the database.
• The relationships among the data.
• Complete view of the data requirements of the organization,
independent of any storage consideration.
• Represents:
- ∀entities, attributes, relations
- constraints on data
- semantic information on data
- security, integrity information
Supports each external view: any data available to a user must
be contained in, or derivable from the conceptual level.
INTERNAL LEVEL
• Physical representation of the DB on the computer.
• How the data is stored in the database.
• Physical implementation of the DB to achieve optimal run-
time performance and storage space utilization.
- Storage space allocation for data and indexes
- Record description for storage
- Record placement
- Data compression, encryption
What is an explanation of the features of OODBMS?
The system must support complex objects. Object identity must be supported. Objects must encapsulated. The system must support types or classes. The system must support inheritance. The system must avoid premature binding. The system must be computationally complete. The system must be extensible. The system must be able to remember data locations. The system must be able to manage large databases. The system must accept concurrent users. The system must be able to recover from hardware and software failures. Data query must be simple.
Explain the aggregate functions in SQL with examples?
Aggregate Functions in SQL Part 1: Introducing SUM and AVGMore of this Feature• Part 2: Counting Records
• Part 3: Max and Min
Join the Discussion"Need some assistance or advice? Join us in the About Databases forum."
Mike Chapple
By their very nature, our databases contain a lot of data. In previous features, we've explored methods of extracting the specific data we're looking for using the Structured Query Language (SQL). Those methods worked great when we were seeking the proverbial needle in the haystack. We were able to answer obscure questions like "What are the last names of all customers who have purchased Siberian wool during the slow months of July and August?"
Oftentimes, we're also interested in summarizing our data to determine trends or produce top-level reports. For example, the purchasing manager may not be interested in a listing of all widget sales, but may simply want to know the number of widgets sold this month. Fortunately, SQL provides aggregate functions to assist with the summarization of large volumes of data. In this three-segment article, we'll look at functions that allow us to add and average data, count records meeting specific criteria and find the largest and smallest values in a table.
All of our queries will use the WidgetOrder table described below. Please note that this table is not normalized and I've combined several data entities into one table for the purpose of simplifying this scenario. A good relational design would likely have Products, Orders, and Customers tables at a minimum.Aggregate Functions in SQL Part 1: Introducing SUM and AVGMore of this Feature• Part 2: Counting Records
• Part 3: Max and Min
Join the Discussion"Need some assistance or advice? Join us in the About Databases forum."
Mike Chapple
By their very nature, our databases contain a lot of data. In previous features, we've explored methods of extracting the specific data we're looking for using the Structured Query Language (SQL). Those methods worked great when we were seeking the proverbial needle in the haystack. We were able to answer obscure questions like "What are the last names of all customers who have purchased Siberian wool during the slow months of July and August?"
Oftentimes, we're also interested in summarizing our data to determine trends or produce top-level reports. For example, the purchasing manager may not be interested in a listing of all widget sales, but may simply want to know the number of widgets sold this month. Fortunately, SQL provides aggregate functions to assist with the summarization of large volumes of data. In this three-segment article, we'll look at functions that allow us to add and average data, count records meeting specific criteria and find the largest and smallest values in a table.
All of our queries will use the WidgetOrder table described below. Please note that this table is not normalized and I've combined several data entities into one table for the purpose of simplifying this scenario. A good relational design would likely have Products, Orders, and Customers tables at a minimum.Aggregate Functions in SQL Part 1: Introducing SUM and AVGMore of this Feature• Part 2: Counting Records
• Part 3: Max and Min
Join the Discussion"Need some assistance or advice? Join us in the About Databases forum."
Mike Chapple
By their very nature, our databases contain a lot of data. In previous features, we've explored methods of extracting the specific data we're looking for using the Structured Query Language (SQL). Those methods worked great when we were seeking the proverbial needle in the haystack. We were able to answer obscure questions like "What are the last names of all customers who have purchased Siberian wool during the slow months of July and August?"
Oftentimes, we're also interested in summarizing our data to determine trends or produce top-level reports. For example, the purchasing manager may not be interested in a listing of all widget sales, but may simply want to know the number of widgets sold this month. Fortunately, SQL provides aggregate functions to assist with the summarization of large volumes of data. In this three-segment article, we'll look at functions that allow us to add and average data, count records meeting specific criteria and find the largest and smallest values in a table.
All of our queries will use the WidgetOrder table described below. Please note that this table is not normalized and I've combined several data entities into one table for the purpose of simplifying this scenario. A good relational design would likely have Products, Orders, and Customers tables at a minimum.
Sourced From:
about.com
http://databases.about.com/od/sql/l/aaaggregate1.htm
By their very nature, our databases contain a lot of data. In previous features, we've explored methods of extracting the specific data we're looking for using the Structured Query Language (SQL). Those methods worked great when we were seeking the proverbial needle in the haystack. We were able to answer obscure questions like "What are the last names of all customers who have purchased Siberian wool during the slow months of July and August?"
Oftentimes, we're also interested in summarizing our data to determine trends or produce top-level reports. For example, the purchasing manager may not be interested in a listing of all widget sales, but may simply want to know the number of widgets sold this month. Fortunately, SQL provides aggregate functions to assist with the summarization of large volumes of data. In this three-segment article, we'll look at functions that allow us to add and average data, count records meeting specific criteria and find the largest and smallest values in a table.
All of our queries will use the WidgetOrder table described below. Please note that this table is not normalized and I've combined several data entities into one table for the purpose of simplifying this scenario. A good relational design would likely have Products, Orders, and Customers tables at a minimum.
What are the advantages of supermarket management systems?
it helps to make the supermarket more effective and efficient when holding information about products
Example of database management system?
A large number of database management systems (DBMS) exist. For example: Oracle, MySQL, DB2.
me2
What is the building block of a relational database?
I think "TABLE" is the main building block of relational database
