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
At times, customers make mistakes in submitting their orders and call to cancel the order. Brewbean’s wants to create a trigger that automatically updates the stock level of all pr

Table Represents an Extension - SQL It describes how each tuple in a relation represents a true instantiation of some predicate and each true instantiation is represented by s

Need Azure CRM Web Application with two-factor authentication We presently have a CRM-like database stored on MS Azure that we presently access over an MS Access application. It

Write a pl/sql block that declares and uses cursors with parameters. In a loop, use a cursor to retrieve the department number and the department name from the departments table

Using INNER JOIN INNER JOIN is used to retrieve the data from all tables listed based on a condition of equality listed after keyword ON. If the condition is not meet, rows ar

Example of EXCEPT Operator - SQL Example, like its counterpart in the theory book, illustrates the convenience of allowing any table expression to be the source for an INSERT

set serveroutput on declare a number(5); b number(5); c number(5); begin a:=&a; b:=&b; c:=a/b; dbms_output.put_line(c); exception when zero_divide then d

Negation (NOT, ¬) - SQL There are three rows instead of just two. As you can see, ¬ p is defined as in two-valued logic (2VL) when p is either true or false, but ¬ (unknown) i

Information Hiding   With the information hiding, you see only the details that are significant at a given level of algorithm and data structure design. The Information hiding

MECHANISTI S THEORY-HAECKEL (1866) - Haeckel stating that after each catalysm, some new organism suddenly forms as a chance event in one stride from inanimate matter and sub