0
Generally relational models are queried using relational algebras. SQL and XQuery are examples of relational algebras, with XQuery actually being a purer form of a relational algebra. : XQuery :: + Already exists and supports this extended relational model :: + Supports XPath :: + Supported by Oracle, IBM and Microsoft databases :: + Existing open source implementations for those who don't have it :: - Not yet a standard (but probably will be) :: - Not very easy to formulate :: - Immature development bindings usually resulting in DOM manipulation (not very efficient) :: - Difficult language to optimize which may result in poor performance :: - No developer community :: - No developer tools :: - It's currently a read-only language and the update additions are not focused on transactional systems : SQL :: + Millions of developers know (and love) it :: + Most repositories already support it :: + Supports PROJECTION, JOIN and UNION :: + Long established standard :: + Efficient language bindings with JDBC and ODBC :: + Lots of development tools :: - Need to specify and implement HIERARCHY ENUMERATION :: - Need to work around the multi-value problem with PROJECTION and SELECTION functions
What else can I help you with?
Why relational algebra is a procedural query language?
The syntax of a query in relational algebra essentially describes the query evaluation algorithm i.e. SELECT WHERE FROM --------------- 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. Please see the link.
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 the difference between T-sql and sql?
T-SQL is Microsoft's version of the generic SQL langauge to be used with, for example, Microsoft SQL Server.
In SQL what is the function of the union operator?
In SQL, the function of the union operator is to combine the result of two or more select-statements. The union operator is a very useful tool when coding SQL.
Why not allow database programmers to write directly in relational algebra instead of sql?
I would guess the SQL language was considered to be simpler for the programmer.
What is Procedural query language?
A procedural language is nothing but what we call relational algebra. Procedural language is just like SQL but with different syntax. In Procedural language for "Select" we use projection and for "where" clause we use selection.
Why relational algebra is a procedural query language?
The syntax of a query in relational algebra essentially describes the query evaluation algorithm i.e. SELECT WHERE FROM --------------- 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. Please see the link.
What is an example of an access relational database?
There is no such thing as an 'Access' Relational Database.A Relational Database Management System is one that has been built to deliver the requirements set out by Edgar Codd in 1970 such that the functions provided by the software conform to relational algebra. This means that the validity actions of the database management system over the data contained in it can be modeled and proved on a mathematical basis.Oracle, DB2, SQL Server, MySQL, etc. all implement most of the requirements of Codd's paper.It is worth noting that the relational model is the ONLYone where the affects of putting data in it can be proven.
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.
A query language for relational databases?
SQL (Structured Query Language) is a standard language used to communicate with and manipulate relational databases. It allows users to retrieve, insert, update, and delete data from databases using specific syntax and commands. SQL is used widely by database administrators, developers, and data analysts for managing and querying relational databases efficiently.
What advantages of QBE compared to SQL?
QBE is an advantage over SQL as it is a visual technique allowing non-experts to do searches, as it is simple to understand.
What has the author Jonathan Leffler written?
Jonathan Leffler has written: 'Using INFORMIX-SQL' -- subject(s): Informix-SQL, Relational databases
What are the differences between Oracle and SQL?
Oracle is an RDBMS aka Relational Database Management System and SQL (Structured Query Language) is a programming language.
What has the author Mary Pyefinch written?
Mary Pyefinch has written: 'SQL from the ground up' -- subject(s): Relational databases, SQL (Computer program language)
What are advantages of rdbms over dbms?
Some advantages of relational database management systems (RDBMS) over traditional database management systems (DBMS) include data integrity through the use of constraints, normalization to reduce redundancy, support for ACID transactions, and standardized SQL language for data manipulation. RDBMS also offer scalability and flexibility for complex data structures and relationships.
What kind of database exist?
The two major commercial classes of database are; relational and non-relational. Example of non-relational databases include Informix c-isam and dbisam. The main relational databases are; MS SQL Server, Sybase, Oracle, Progress, mySQL.
