Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Indeterminacy in SQL
Some SQL expressions are actually not function invocations at all in the mathematical sense, being indeterminate-invocations operating on identical input do not always yield the same value. The indeterminate expressions are among those that the standard defines as possibly non-deterministic, but- caveat lector-not all expressions defined as possibly non-deterministic are actually indeterminate from a mathematical viewpoint. For example, the key word USER denotes the userid (officially, the authorization identifier) of the session in which an expression containing that key word is evaluated. Such an expression is defined as possibly non-deterministic by virtue of the appearance of USER, even though invocations in different sessions, in which USER stands for different userids, are clearly different invocations.
For a more general example, a user-defined function can be explicitly declared as either DETERMINISTIC or NOT DETERMINISTIC. In the latter case the "function" is flagged such that all invocations of it are treated as possibly non-deterministic. Regardless of the appropriateness of the term non-deterministic, there is a good reason for categorizing references to the current user (or, for another example, the current time) along with genuine cases of indeterminacy. It concerns constraint declarations. We clearly want to outlaw a constraint condition whose result, when evaluated, depends on the properties of the session in which, or on the time at which, the evaluation takes place. Of course we must also outlaw genuinely indeterminate conditions-a database might satisfy such a condition but later fail to satisfy it even though the database has not been updated in the meantime! The question then arises as to how it is possible for indeterminacy to arise: surely a computer program always gives the same result when invoked with the same input?
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
%FOUND Until the SQL data manipulation statement is executed, the %FOUND yields NULL. Afterward, the %FOUND yields TRUE, when an INSERT, UPDATE, or DELETE statement affected o
Functions The function is a subprogram which can take parameters and be invoked. Normally, you can use a function to calculate a value. The function has 2 sections: the specifi
Constants and Variables: You can declare the constants and variables in the declarative section of any PL/SQL subprogram, block, or package. The Declarations allot the stor
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
First Step at defining type SID in SQL CREATE TYPE SID AS ( C VARCHAR(5) ) ; Explanation: TYPE SID announces that a type named SID is being defined to the syst
Using LIMIT For nested tables, that have no maximum size, the LIMIT returns NULL. For varrays, the LIMIT returns the maximum number of elements that a varray can have (that yo
Using %ROWTYPE The %ROWTYPE attribute gives a record type which represents a row in a table (or view). The record can store the whole row of data selected from the table or fetc
Due to an increase in overhead costs, the buying price of all items needs to be increased. Management wants to see a report before deciding how much each product will go up. Add to
Count Operator in SQL Example: Counting the students who have scored more than 50 in some exam (SELECT COUNT (*) FROM (SELECT DISTINCT StudentId FROM EXAM_MARK WHE
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd