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?
V ariables and Constants in PL/SQL The PL/SQL permits you to declare constants and variables, and then use them in SQL and procedural statements anywhere in the expression. Th
Fetching Across Commits The FOR UPDATE clauses acquire exclusive all row locks. All rows are locked when you open the cursor, and when you commit your transaction they are unl
Majority of Differences among 9i, 10G, 11G :- These are some combine feature which has differences among others. Automatic Workload Repository (AWR) Drop database' s
Use External Routines The PL/SQL is particular for the SQL transaction processing. Therefore, several tasks are more quickly completed in a lower-level language like C that is
Declaring Objects: You can use the object types wherever built-in types like CHAR or NUMBER can be used. In the block below, you can declare object r of type Rational. Then, yo
Parameter Modes To define the behavior of formal parameters you use the parameter modes. The 3 parameter modes, IN, OUT, & IN OUT, can be used with any subprogram. Though, a
Data Types in SQL - Interval, Boolean INTERVAL for values denoting, not intervals (!) but durations in time, such as 5 years, 3 days, 2 minutes, and so on. BOOLEAN, con
Fetching with a Cursor The FETCH statements retrieve the rows in the result set one at a time. After each and every fetch, the cursor advance to the next row in the result set
Using a Host Variable You can declare the cursor variable in the PL/SQL host environment like an OCI or Pro C program. To use the cursor variable, you should pass it as a host
Components of an Object Type: An object type encapsulates the operations and data. Therefore, you can declare the methods and attributes in an object type specification, but no
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