Relational Algebra - SQL

It describes some operators, that together constitute an algebra that is not only relationally complete but also irreducibly so (very nearly- apart from RENAME, which can be expressed in terms of extension and projection, none of those operators can be discarded without sacrificing completeness). We can use these operators as a basis for testing SQL for relational completeness. If we can show that for every invocation of one of these operators there is an equivalent SQL expression, then we will have shown that SQL is relationally complete. By "equivalent" we mean an expression whose table operands are counterparts of the relation operands (ignoring the ordering that SQL imposes on the columns) and whose result is a table counterpart result, where a table is a counterpart of a relation if and only if it satisfies all of the following conditions:

• Every column has a name
• No two distinct columns have the same name
• No row appears more than once
• Null doesn't appear in place of a value anywhere in the table
• Every row consists entirely of its column values and doesn't somehow contain any additional data

Posted Date: 1/18/2013 4:26:49 AM | Location : United States

Ask an Expert

Related Discussions:- Relational algebra - sql, Assignment Help, Ask Question on Relational algebra - sql, Get Answer, Expert's Help, Relational algebra - sql Discussions

Write discussion on Relational algebra - sql
Your posts are moderated

Write your message here..

Related Questions

Between operator-comparison operators, BETWEEN Operator The operator BET... BETWEEN Operator The operator BETWEEN, tests whether the value lies in a specified series. That means "greater than or equivalent to low value and less than or equivalent to hig

Calculate the number of tuples, Question: (a) The objective of query opti... Question: (a) The objective of query optimization is to choose the most efficient strategy for implementing a given relational query, thereby improving the system performance. On

Controlling autonomous transactions, Controlling Autonomous Transactions ... Controlling Autonomous Transactions The first SQL statement in an autonomous routine starts a transaction. Whenever one transaction ends, the next SQL statement starts the oth

Obtaining a natural join by specifying the common columns, Obtaining a natu... Obtaining a natural join by specifying the common columns Synatax: SELECT * FROM IS_CALLED JOIN IS_ENROLLED_ON USING ( StudentId ) However, a named columns join doe

Union and or - sql, UNION and OR - SQL SQL supports UNION explicitly b... UNION and OR - SQL SQL supports UNION explicitly but differently from the way it supports JOIN explicitly. As we have seen, JOIN is used exclusively within the FROM clause, su

Insert command in sql, INSERT Command in SQL Loosely speaking, INSERT... INSERT Command in SQL Loosely speaking, INSERT takes the rows of a given source table and adds them to the specified target table, retaining all the existing rows in the targ

Origin of earth - big bang hypothesis, ORIGIN OF EARTH - BIG-BAN G HY... ORIGIN OF EARTH - BIG-BAN G HYPOTHESIS - Origin of life is linked to origin of earth. Cosmos, the Universe originated 10-20 billion years ago by Big Bang (thermonu

Declaring cursor variables, Declaring Cursor Variables Once a REF CURS... Declaring Cursor Variables Once a REF CURSOR type is define by you, and then you can declare the cursor variables of that type in any PL/SQL block or subprogram. In the exampl

Execute privilege, EXECUTE Privilege To call an invoker-rights routine ... EXECUTE Privilege To call an invoker-rights routine straightforwardly, the users should have the EXECUTE privilege on that routine. By yielding the privilege, you permit a user

Scope and visibility- pl/sql, Scope and Visibility The References to an ... Scope and Visibility The References to an identifier are resolved according to its visibility and scope. The scope of an identifier is that area of a program unit (subprogram, b