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

Magento change address format depending on store, Magento change address fo...

Magento change address format depending on store Project Description: What I need is that depending on the store in which the customer bought the address should change the fo

Insert command in sql, INSERT Command in SQL Loosely speaking, INSERT...

INSERT Command in SQL Loosely speaking, INSERT takes the rows of a given source table and adds them to the specified target table, retaining all the existing rows in the targ

Declaring and initializing objects in pl/sql, Declaring and Initializing Ob...

Declaring and Initializing Objects: An object type is once defined and installed in the schema; you can use it to declare the objects in any PL/SQL, subprogram, block or packa

Keyword and parameter description - if statement, Keyword and Parameter Des...

Keyword and Parameter Description: boolean_expression: This is an expression which results the Boolean value TRUE, FALSE, & NULL. It is related with a series of statement

Cartesian product, Using a Join on 2 tables, select all columns and all row...

Using a Join on 2 tables, select all columns and all rows from the tables without the use of a Cartesian product. Query: SELECT * FROM EMPLOYEE1 JOIN CONTRACT ON EMPLOYEE

Pl/sql assignment, 1. a. Write a trigger that fires when a part's price...

1. a. Write a trigger that fires when a part's price is updated. The trigger will write a record into a table called PriceUpdates. The record should contain the information of

Keyword & parameter description - exceptions, Keyword & Parameter Descripti...

Keyword & Parameter Description: WHEN: This keyword introduces the exception handler. You can have many exceptions execute the similar sequence of the statements by follo

Forall statement - syntax, FORALL Statement The FORALL statements instr...

FORALL Statement The FORALL statements instruct the PL/SQL engine to bulk-bind the input collections before sending them to the SQL engine. Though the FORALL statement consists

Avoiding collection exceptions, Avoiding Collection Exceptions   In ma...

Avoiding Collection Exceptions   In many cases, if you reference a nonexistent collection element, then PL/SQL raises a predefined exception. Consider the illustration shown b

Procedures - syntax, Procedures The procedure is a subprogram which can...

Procedures The procedure is a subprogram which can take parameters and be invoked. Normally, you can use a procedure to perform an action. The procedure has 2 sections: the spe

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