Third step at defining type sid in sql, PL-SQL Programming

Assignment Help:

Third Step at defining type SID in SQL

CREATE DOMAIN SID AS VARCHAR(5)

CHECK ( VALUE IS NOT NULL AND

SUBSTRING(VALUE FROM 1 FOR 1) = 'S' AND

CAST('+'||SUBSTRING(VALUE FROM 2) AS INTEGER) >= 0 );

Explanation:

  1. DOMAIN SID announces that a domain named SID is being defined to the system.
  2. AS VARCHAR(5) specifies that values in domain SID are certain values of type VARCHAR(5).
  3. CHECK ( ... ) specifies a constraint defining exactly which values of type VARCHAR(5) are in the domain SID. Note that the key word VALUE, which is available only in domain constraints, refers (in this particular example) to an arbitrary value of type VARCHAR(5).
  4. VALUE IS NOT NULL specifies that the null value of type VARCHAR(5) is not a value in the domain. This is needed because the other conjuncts evaluate to UNKNOWN if VALUE is the null value and a domain constraint is deemed to be violated only when it evaluates to FALSE.
  5. SUBSTRING(VALUE FROM 1 FOR 1) = 'S' specifies that every value in the domain must begin with S. Note SQL's deliberate use of "noise" words in the invocation of SUBSTRING, the justification for which is to distinguish invocations of system-defined operators from those of user-defined ones.
  6. CAST('+'||SUBSTRING(VALUE FROM 2) AS INTEGER) >= 0 is an attempt to emulate an invocation of IS_DIGITS, perhaps showing how a user-defined operator of that name might be implemented in SQL. The character "+" is concatenated to the putatively numeric portion of the string in order to exclude values such as 'S+123' from the domain (the string '+123' can be cast as an integer but '++123' cannot).

Related Discussions:- Third step at defining type sid in sql

In mode - parameter modes, IN Mode An IN parameter pass the values to ...

IN Mode An IN parameter pass the values to the subprogram being called. Within the subprogram, an IN parameter acts like a constant. And hence, it cannot be assigned a value.

Procedural constraint enforcement (triggers) , Procedural Constraint Enforc...

Procedural Constraint Enforcement (Triggers) SQL has an alternative method of addressing database integrity, involving event-driven procedural code. The special procedures th

Updating by replacement, Updating by replacement Syntax: UPDAT...

Updating by replacement Syntax: UPDATE ENROLMENT SET Name = 'Ann' WHERE StudentId = SID ('S1'); Note the use of SET, as already noted in connection with direct a

Example of null operator - nino rule, Example of Null operator - NiNo Rule ...

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 sho

Object types - syntax, Object Types An object type is a user-defined co...

Object Types An object type is a user-defined complex datatype which encapsulates the data structure along with the functions and procedures required to manipulate the data. Th

Procedures in pl/sql, Procedures   The procedure is a subprogram which...

Procedures   The procedure is a subprogram which performs a specific action. You write procedures using the syntax as shown below: PROCEDURE name [(parameter[, parameter, .

Write a pl/sql anonymous block that accepts an employee id, Based on the EM...

Based on the EMPLOYEE table created in Assignment #1, write a PL/SQL anonymous block that accepts an employee ID from the user input and finds whether the employee ID is in the EMP

Mutual recursion, Mutual Recursion The Subprograms are mutually recursi...

Mutual Recursion The Subprograms are mutually recursive if they directly or indirectly call each other. In the illustration below, the Boolean functions odd & even, that dete

Parameter and keyword description - select into statement, Parameter and Ke...

Parameter and Keyword Description: select_item: This select_item is a value returned by the SELECT statement, and then assigned to the equivalent variable or field in the

Oracle PL SQL, I need to write one function and one procedure to query a Or...

I need to write one function and one procedure to query a Oracle 10.1 DB using PL SQL. I have the schema and exact queries...along with work Ive started and a template to put the a

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