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The syntax of a query in relational algebra essentially describes the query evaluation algorithm i.e. SELECT WHERE FROM
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I don't agree with the above answer.
Notice that 'SELECT WHERE FROM' is fragmentary SQL. It does not describe an algorithm, or procedure, for obtaining the desired results. Rather, it describes the characteristics of the desired results and where they might be obtained.
In fact, relational algebra is not inherently procedural. It involves closed collections of objects called relations and a set of permitted operations on these objects.
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Why do you use Linq over SQL Statements?
The extensibility of the query architecture is used in the LINQ project itself to provide implementations that work over both XML and SQL data. The query operators over XML (LINQ to XML) use an efficient, easy-to-use, in-memory XML facility to provide XPath/XQuery functionality in the host programming language. The query operators over relational data (LINQ to SQL) build on the integration of SQL-based schema definitions into the common language runtime (CLR) type system. This integration provides strong typing over relational data while retaining the expressive power of the relational model and the performance of query evaluation directly in the underlying store.
What is the difference in Sql statement of sql and of relation algebra?
In essence, Relational Algebra shows the mathematical manner in which a database management system (DBMS) goes about its job. Through the use of Relational Algebra, we can calculate the most efficient way for a DBMS to interact with the database, e.g. updating records, performing a COUNT of the rows in a table etc. The Relational Algebra for returning the surnames in a table holding details of employees where their salary is greater than 30000 per year, is as follows: SELECTSurname(PROJECTSalary>30000) (The SELECT operator is often a Pi symbol, and the PROJECT operator is often a Sigma symbol) An SQL statement, however, would go something like this: SELECT Surname FROM tblEmployee WHERE Salary>30000 Hopefully you can see the difference. Ultimately, the algebra can be used by mathematicians and DBMS creators to ensure the DBMS works as efficiently as possible in performing tasks required by users. Whilst not really necassary in a small-scale database, clearly in a large, complex database you'll be looking at thousands and thousands of rows that need to be queried, updated etc, so efficiency in getting the data back is very important! An SQL statement may look similar, but there's no real calculation involved here. It is instead a standardised language allowing database administrators and users to give a set of instructions, telling the DBMS (Oracle, MS Access, MySQL etc.) what you want to do to a database, e.g. query it, update it, delete from it, and so on. I hope that answers your question!
What is a relational database query and Explain with an example?
A relational database matches data by using common characteristics found within the data set. The resulting groups of data are organized and are much easier for many people to understand.For example, a data set containing all the real-estate transactions in a town can be grouped by the year each transaction occurred, the sale price, a buyer's last name and so on. Such a grouping uses the relational model (a technical term for this is schema). Hence, such a database is called a "relational database."The software used to do this grouping is called a relational database management system (RDBMS). The term "relational database" often refers to this type of software.Relational databases are currently the predominant choice in storing data like financial records, medical records, personal information and manufacturing and logistical data.
Difference between SQL and OQL?
in some cease both are the same they use query language but in fact the out puts are very deference
What is a correlated query?
Correlated query has a subquery in it which accesses the column name of a table alias which is outside the subquery.
