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SQL
SQL Meaning
SQL (Structured Query Language)is a specialized programming language designed for managing and manipulating data stored in relational databases. It allows users to perform various operations such as querying, updating, inserting, and deleting data efficiently12.
Key Principles of SQL
Declarative Language: SQL is a declarative language, meaning it specifies what data to retrieve or manipulate rather than how to perform the operation. This makes it easier to use and understand1.
Standardization: SQL became a standard of the American National Standards Institute (ANSI) in 1986 and the International Organization for Standardization (ISO) in 19872.
Components: SQL consists of several sublanguages, including Data Query Language (DQL), Data Definition Language (DDL), Data Control Language (DCL), and Data Manipulation Language (DML)1.
Common SQL Commands
SELECT: Retrieves data from a database.
INSERT: Adds new records to a database.
UPDATE: Modifies existing records.
DELETE: Removes records from a database.
CREATE: Creates new database objects like tables and views.
ALTER: Modifies existing database objects.
Example of a Simple SQL Query
SELECT*FROMCustomersWHERECustomerNameLIKE'J%'ORDER BYCustomerIDDESCLIMIT 10;
This query retrieves the top 10 customers whose names start with 'J', ordered in descending order by their customer ID3.
Uses of SQL
SQL is widely used across various industries and applications, including:
Data Retrieval: Extracting data from databases for analysis and reporting.
Data Manipulation: Adding, updating, and deleting data in databases.
Data Definition: Defining the structure and organization of data in databases.
Access Control: Managing user permissions and ensuring data security23.
Important Considerations
Interoperability: SQL implementations can vary between different database systems, leading to compatibility issues1.
Security: SQL injection is a common security vulnerability where malicious SQL code is inserted into queries to manipulate or corrupt data3.
In conclusion, SQL is a powerful and versatile language for managing relational databases, offering a wide range of functionalities for data manipulation, retrieval, and security12.
Devon(/ˈdɛvən/, also known asDevonshire) is acountyofEngland, reaching from theBristol Channelin the north to theEnglish Channelin the south. It is part ofSouth West England, bounded byCornwallto the west,Somersetto the north-east andDorsetto the east. The city ofExeteris thecounty town. The county includes the districts ofEast Devon,Mid Devon,North Devon,South Hams,Teignbridge,TorridgeandWest Devon.PlymouthandTorbayare each geographically part of Devon, but are administered asunitary authorities.[4]Combined as aceremonial county, Devon's area is 6,707 km2(2,590 square miles)[5]and its population is about 1.1 million.
Devon derives its name fromDumnonia(the shift frommtovis a typicalCeltic consonant shift). During theBritish Iron Age,Roman Britainand theearly Middle Ages, this was the homeland of theDumnoniiBrittonicCelts. TheAnglo-Saxon settlement of Britainresulted in the partial assimilation of Dumnonia into theKingdom of Wessexduring the eighth and ninth centuries. The western boundary with Cornwall was set at theRiver TamarbyKing Æthelstanin 936. Devon was later constituted as ashireof theKingdom of England.
The north and south coasts of Devon each have both cliffs and sandy shores, and the county'sbayscontainseaside resorts,fishing townsandports. The inland terrain is rural, generally hilly and has a lower population density than many other parts of England.Dartmooris the largest open space in southern England, at 954 km2(368 square miles);[6]itsmoorlandextends across a large expanse ofgranitebedrock. To the north of Dartmoor are theCulm MeasuresandExmoor. In the valleys and lowlands of south and east Devon the soil is more fertile, drained by rivers including theExe, theCulm, theTeign, theDartand theOtter.
As well as agriculture, much of theeconomy of Devonis based ontourism. The comparatively mild climate, coastline and landscape make Devon a destination forrecreation and leisure in England. Visitors are particularly attracted to the Dartmoor and Exmoornational parks; its coasts, including the resort towns along the south coast known collectively as theEnglish Riviera; theJurassic CoastandNorth Devon's UNESCO Biosphere Reserve; and the countryside including theCornwall and West Devon Mining Landscape.
