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History of SQL Database
In 1969, IBM researcher Edgar F. Codd defined the relational database model, which became the basis for developing the SQL language. This model is built on common pieces of information (or “keys”) being associated with various data. For example, a username might be associated with an actual name and a telephone number.
A few years later, IBM began working on a new language for relational database management systems based on Codd’s findings. The language was originally called SEQUEL, or Structured English Query Language. Dubbed System/R, the project went through a few implementations and revisions, and the name of the language changed several times before finally landing on SQL.
After beginning testing in 1978, IBM started developing commercial products, including SQL/DS (1981) and DB2 (1983). Other vendors followed suit, announcing their own commercial SQL-based offerings. These included Oracle, which released its first product in 1979, as well as Sybase and Ingres.
Learning 0f SQL Database
It typically is easier for beginners to learn SQL than it is for them to pick up programming languages like Java, C++, PHP, or C#.
Several online resources—including free tutorials and paid distance learning courses—are available for those who have little programming experience but want to learn SQL. Formal university or community college courses also will provide a deeper understanding of the language.
Some of the free tutorials include W3Schools SQL Tutorial, SQLcourse.com, and Codecademy’s Learn SQL and a course on analyzing SQL business metrics.
Options for paid distance-learning courses include the International Webmasters Association’s (IWA) Introduction to SQL (Using Access) or Introduction to SQL (Using MySQL). IWA’s SQL courses are only four weeks long, but the presence of instructors and weekly assignments make them more structured than self-learning tutorials.
Useful books on SQL for beginners include “SQL: A Beginner’s Guide” and “SQL in a Nutshell.”
Some Important Questions about SQL Database are listed below:
1- What is the use of CASCADE CONSTRAINTS?
2- Which function is used to find the largest integer less than or equal to a specific value?
3- What is the output of the following query?
SELECT TRUNC(1234.5678,-2) FROM DUAL;
4- Which is the subset of SQL commands used to manipulate Oracle Database structures, including tables?
5- What operator performs pattern matching ?
6- What operator tests column for the absence of data?
7- Which command executes the contents of a specified file?
8- What is the parameter substitution symbol used with INSERT INTO command?
9-Which command displays the SQL command in the SQL buffer, and then executes it?
10- What are the wildcards used for pattern matching?
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