Substitution and instantiation - sql, PL-SQL Programming

Substitution and Instantiation - SQL

It shows how NULL might appear in substitution for a parameter of a predicate and how it might thus participate in instantiation of that predicate to yield a proposition. Now consider instantiations of the dyadic predicate a < b. As well as instantiations such as 5 < 10 (a true one) and 9 < 6 (a false one), we now have to entertain the possibility of instantiations such as 5 < NULL, NULL < 6, and NULL < NULL.

In SQL these comparisons evaluate to that intrusive truth value, unknown. It goes on to explain that the extension of a predicate consists exactly of those instantiations of it that evaluate to true, from which we can conclude, of every instantiation that does not appear in the extension, that it is false, in which case it must appear instead in the extension of the negation of that predicate. In SQL, then, the instantiation 5 < NULL, for example, cannot be considered to appear in either the extension of a < b or NOT (a < b). Or so it would appear.

Posted Date: 1/18/2013 3:08:44 AM | Location : United States







Related Discussions:- Substitution and instantiation - sql, Assignment Help, Ask Question on Substitution and instantiation - sql, Get Answer, Expert's Help, Substitution and instantiation - sql Discussions

Write discussion on Substitution and instantiation - sql
Your posts are moderated
Related Questions
a. Create a table odetails_new. It has all the attributes of odetails and an additional column called cost, whose values are the product of the quantity and price of the part bein

COMMIT Statement The COMMIT statement explicitly makes everlasting changes to the database during the present transaction. The Changes made to the database are not considered e

Main features of PL/SQL A good way to get familiar with PL/SQL is to look at a sample program. The below program processes an order for tennis rackets. At first, it declares a

Query: SELECT * FROM EMPLOYEE1; Select 5 columns and all rows from one table Query: SELECT C_ID, COMPANY, BUILDING, DEPARTMENT, BRANCH FROM CONTRACT;

Synonyms You can create the synonyms to provide location transparency for the remote schema objects like tables, views, sequences, stand-alone subprograms, and packages. Though,

Data Types in SQL - Integer INTEGER or  synonymously INT, for integers within a certain range. SQL additionally has types SMALLINT and BIGINT for certain ranges of integers. T

I need a query for PL/SQL, selecting names with cursor, goes down the list, assigns usernames (initials001) based on initials in the name. If two names have same initials the user

Exception handling In the PL/SQL, a warning or error condition is known as an exception. The Exceptions can be internally defined (by the run-time system) or user defined. The

How Exceptions Propagate ? Whenever an exception is raised, and if the PL/SQL cannot find a handler for it in the present subprogram or block, the exception propagates. That is

Overloading The PL/SQL overloads the subprogram names. That is, you can use similar name for few different subprograms as long as their formal parameters differ in the number