Example of null operator - nino rule, PL-SQL Programming

Assignment Help:

Example of Null operator - NiNo Rule

If we wanted to make HIGHER_OF adhere to "NULL in, NULL out"-let's call it the NiNo rule-we would have to write something like what is shown in Example 2.1a.

Example: NiNo version of HIGHER_OF

CREATE FUNCTION HIGHER_OF ( A INTEGER, B INTEGER )

RETURNS INTEGER

CASE

WHEN A IS NULL OR B IS NULL

THEN RETURN CAST (NULL AS INTEGER);

WHEN A > B

THEN RETURN A;

ELSE RETURN B;

END CASE;

Explanation:

  • IS NULL is a monadic Boolean operator that evaluates to TRUE when its argument is "the null value", otherwise FALSE. Note, therefore, that it is our first exception to the NiNo rule, which would require it to evaluate to NULL (UNKNOWN) when its argument is "the null value".
  • CAST (NULL AS INTEGER) denotes "the null value" of type INTEGER. As in Tutorial D, the operand of RETURN must be an expression that has a declared type and NULL, on its own, does not have a declared type. The CAST operator takes an expression and a type name, separated by the "noise" word AS, and normally expresses a "type conversion"-a function that maps elements of one type to those of another that are considered to be in some defined sense equivalent. In the special case of NULL it is used to confer a type, so to speak, on something that doesn't otherwise have one.
  • AS, appearing where you might have expected just a comma, is explained by a matter of policy in SQL whereby invocations of user-defined functions, which always use commas between arguments, can be syntactically distinguished from invocations of system-defined functions.
  • OR is SQL's counterpart of the usual logical operator of that name. In A IS NULL OR B IS NULL its operands are clearly restricted to just TRUE and FALSE and that expression therefore results in TRUE if either of those operands does, otherwise FALSE.

Related Discussions:- Example of null operator - nino rule

Rollback behavior - bulk bind performance improvement, Rollback Behavior ...

Rollback Behavior When a FORALL statement fails, the database changes are rolled back to an implicit savepoint marked before each of the SQL statement execution. The Changes t

Query optimization, 1.( /5 marks) Suppose that a B+-tree index with the sea...

1.( /5 marks) Suppose that a B+-tree index with the search key (dept_name, building) is available on relation department. What would be the best way to handle the following selecti

Special cases of projection, Special cases of projection This section ...

Special cases of projection This section describes the identity projection, r {ALL BUT}, and the projection on no attributes, r { }, which yields TABLE_DUM when r is empty, ot

Exceptions - syntax, Exceptions An exception is the runtime error or wa...

Exceptions An exception is the runtime error or warning condition that can be predefined or user-defined. The Predefined exceptions are raised implicitly through runtime system

Keyword and parameter description - forall statement, Keyword &Parameter De...

Keyword &Parameter Description: index_name: This is an undeclared identifier which can be referenced only within the FORALL statement and only as the collection subscript

Manipulating objects in pl sql, Manipulating Objects: You can use an o...

Manipulating Objects: You can use an object type in the CREATE TABLE statement to indicate the datatype of a column. When the table is created once, you can use the SQL statem

Select query, Query: SELECT * FROM EMPLOYEE1; Select 5 columns and ...

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

Forward declarations - subprograms, Forward Declarations The PL/SQL ne...

Forward Declarations The PL/SQL needs that you declare an identifier before using it. And hence, you should declare a subprogram before calling it. For illustration, the decla

Create a procedure to tax calculation task, Complete the following steps to...

Complete the following steps to create a procedure to calculate the tax on an order. The BB_TAX table contains the states that require taxes to be submitted for Internet sales. If

Fetching from a cursor variable, Fetching from a Cursor Variable The F...

Fetching from a Cursor Variable The FETCH statement retrieve rows one at a time from the product set of a multi-row query. The syntax for the same is as shown: FETCH {curso

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd