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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 else can I help you with?
What is the difference between a statement and a clause in SQL?
An SQL statement is a complete set of clauses which returns a value and ends with a semicolon(;) A statement is made up of several clauses Ex: select * from person where f_name='me'; In this ex ' select * from person where f_name='me';' is the statement and select*, from person, where f_name= are the clauses
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.
What is the difference between quel SQL and qbe?
gand maro...is the answer
Difference between alter and update commands in sql?
Update and Alter are two SQL (Structured Query Language) commands used for modifying databases. Update statement is used to update existing records in a database. Update is a Data Manipulation Language (DML) statement. Alter SQL command is used to modify, delete or add a column to an existing table in a database. Alter is a Data Definition Language (DDL) statement.Commands that are used to define the structure of a database (database schema) are called DDL statements.
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 the difference between a statement and a clause in SQL?
An SQL statement is a complete set of clauses which returns a value and ends with a semicolon(;) A statement is made up of several clauses Ex: select * from person where f_name='me'; In this ex ' select * from person where f_name='me';' is the statement and select*, from person, where f_name= are the clauses
What are the reasons for converting SQL queries into relational algebra queries?
Converting SQL queries into relational algebra queries can enhance understanding of the underlying operations and data manipulation processes. It provides a more abstract representation of query execution, helping to optimize performance by identifying potential inefficiencies in the SQL statement. Additionally, relational algebra serves as a foundational theoretical framework for database theory, aiding in the formal analysis and optimization of database queries. Finally, it facilitates the translation of queries across different database systems by providing a common operational language.
What are the differences between SQL statement to iSQL plus statement?
Structured Query Lanaguage(SQL) is a command language to communicate with oracle server.whereas SQL*PLUS is an oracle tool that recognises and submits sql statements to the oracle server for execution.
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 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.
What is the difference between hql and sql?
one of the difference is HQL does not support distinct but SQL supports the distinct in the query
What is the error in this SQL statement?
You need to tell us what the statement is - in order for us to help you !
What is the abbreviation for statement?
Statement can be abbreviated to STMT. It is not widely used, but it appears SQL code.
What does a SQL Delete statement allow?
An SQL Delete statement is a code used for programming. It allows you to delete a single record or multiple records from a graph or table. These codes can be very useful.
Difference between sql server 2003 sql server 2005?
There is no such thing as SQL Server 2003. Microft released SQL Server 2005 as the next version of SQL Server 2000.
What SQL clause is used to determine the fields to be displayed in an SQL Query statement?
The SQL clause used to determine the fields to be displayed in an SQL query statement is the SELECT clause. It specifies the columns or expressions that the query will return from the database. For example, SELECT column1, column2 FROM table_name; retrieves the specified columns from the given table.
Which sql statement is used to update data from a database?
The SQL statement used to update data in a database is the UPDATE statement. It allows you to modify existing records in a table by specifying the columns and values to be updated based on certain conditions.
