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

Important distinctions, Important Distinctions The list of important d...

Important Distinctions The list of important distinctions are given below: Value versus variable Syntax versus semantics Variable versus variable reference

Implicit cursors, Implicit Cursors The Oracle implicitly opens a curso...

Implicit Cursors The Oracle implicitly opens a cursor to process each SQL statement not related with an explicitly declared cursor. The PL/SQL lets you refer to the most recen

Program, heap sort program in pl/sql

heap sort program in pl/sql

Manipulating individual elements - pl/sql, Manipulating Individual Elements...

Manipulating Individual Elements Faraway you have manipulated an entire collection. Within the SQL, to manipulate the individual elements of the collection, and then use the ope

Write an anonymous block that contains a pl/sql procedure, Write an anonymo...

Write an anonymous block that contains a PL/SQL procedure. The procedure takes two input parameter: oldZip and newZip, and it updates the zipcodes table by replacing all oldZip wit

Rowid - sql pseudocolumns, ROWID The ROWID returns the rowid (binary a...

ROWID The ROWID returns the rowid (binary address) of a row in the database table. You can use the variables of the type UROWID to store rowids in a readable format. In the il

Declaring cursor variables, Declaring Cursor Variables Once a REF CURS...

Declaring Cursor Variables Once a REF CURSOR type is define by you, and then you can declare the cursor variables of that type in any PL/SQL block or subprogram. In the exampl

Goto statement - syntax, GOTO Statement   The GOTO statement branches ...

GOTO Statement   The GOTO statement branches categorically to a block label or statement label. The label should be exclusive within its scope and should precede a PL/SQL bloc

Obtaining a natural join by specifying the common columns, Obtaining a natu...

Obtaining a natural join by specifying the common columns Synatax: SELECT * FROM IS_CALLED JOIN IS_ENROLLED_ON USING ( StudentId ) However, a named columns join doe

Procedure, 1. Create a procedure called TAX_COST_SP to accomplish the tax c...

1. Create a procedure called TAX_COST_SP to accomplish the tax calculation task. Keep in mind that the state and subtotal values are inputs into the procedure and the procedure is

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