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!
Cause of Indeterminacy in SQL
One root cause of indeterminacy in SQL lies in its implementation of comparison for equality. For certain system-defined types it is possible for distinct values to compare equal (note the contradiction). One such type is CHARACTER. Like COBOL, SQL ignores trailing "pad characters" when comparing character strings. The pad character is normally the space obtained by depressing the space bar on a keyboard. Thus, for example, the comparison 'SQL' = 'SQL ' evaluates to TRUE, even though CHAR_LENGTH('SQL') = CHAR_LENGTH('SQL '), comparing the lengths of those two strings, 3 and 6, evaluates to FALSE. Now consider the relational projection of ENROLMENT over just its Name attribute: ENROLMENT{Name} has a counterpart of projection, but suppose the two rows for student S1 in the ENROLMENT table had 'Anne' and 'Anne ' for S1's name.
If both of those values were to appear in the result, that would be inconsistent with the fact that they compare equal in SQL. If just one of them appears, then which one? The SQL standard declares such an expression to be possibly non-deterministic and permits a conforming implementation to give any value that compares equal to 'Anne'-possibly one that doesn't even appear in the table-and does not require it to give the same value every time the expression is evaluated. As a consequence, there are several SQL operators whose use on character strings is not permitted to appear in constraint declarations. The SQL standard lists a multitude of conditions that cause an expression to be defined as possibly non-deterministic. Perhaps the most alarming is the assumption that equals comparison of values of user-defined types is assumed to suffer from the same problem as I have described for character strings: it is assumed that distinct values can compare equal, even if the type definition is such that this cannot possibly be the case.
Packages The package is a schema object which groups logically associated to the PL/SQL items, types, and subprograms. The Packages have 2 sections: the specification & the bod
Deriving Predicates from Predicates in SQL The corresponding section in the theory book describes how predicates can be derived from predicates using (a) the logical connectiv
Advantages of Wrapping The PL/SQL Wrapper convert the PL/SQL source code into a transitional form of the object code. By hiding the application internals, the Wrapper secure
The SQL ‘CREATE TABLE' scripts for all the tables you have implemented. Note that your tables must correspond exactly to the ERD you have provided in 1. above, or you will lose ma
Pass the nulls to a dynamic SQL: Passing Nulls: Assume that you want to pass the nulls to a dynamic SQL statement. For illustration, you may write the EXECUTE IMMEDIATE
THEO R Y OF ETERNITY OF LIFE (PRAYER - 1880) - The theory of eternity of life, also called the steady-state theory , states that life has ever been in existence as at presen
Operators on Tables and Rows Row Extraction TUPLE FROM r, SQL has row subqueries. These are just like scalar subqueries except that they may specify more than one column.
PITS Depressions in secondary cell wall is called pit. A pit present on the free cell wall surface without its partner is called Blind pit. It consists of 2 parts -
Varrays versus Nested Tables The Nested tables are differing from varrays in the following ways: 1) Varrays have a maximum size, while nested tables do not. 2) Varrays are
Logical Operators The logical operators AND, NOT, and OR follow the tri-state logic shown in table below. The AND and OR are binary operators; NOT is a unary operator.
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