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

Using operator ref - manipulating objects pl sql, Using Operator REF: ...

Using Operator REF: You can retrieve refs by using the operator REF that, like VALUE, takes as its argument a correlation variable. In the illustration below, you retrieve one

Dynamic sql - pl sql, Dynamic SQL: The Most PL/SQL programs do a predi...

Dynamic SQL: The Most PL/SQL programs do a predictable, specific job. For illustration, a stored procedure may accept an employee number and salary increase, and then update t

Cursors in pl/sql, Cursors The Oracle uses work areas to execute the SQ...

Cursors The Oracle uses work areas to execute the SQL statements and to store process information. A PL/SQL construct known as the cursor. Let's you assume name a work area and

Sql functions, SQL Functions The PL/SQL uses all the SQL functions invo...

SQL Functions The PL/SQL uses all the SQL functions involving the following aggregate functions that summarize the whole columns of the Oracle data: GROUPING, AVG, COUNT, STDDE

Keyword & parameter description - expressions, Keyword & Parameter Descript...

Keyword & Parameter Description: boolean_expression: This is an expression which yields the Boolean value that is TRUE, FALSE, & NULL. character_expression: This

Update statement - syntax, UPDATE Statement   The UPDATE statement tra...

UPDATE Statement   The UPDATE statement transforms the values of the specified columns in one or more rows in the table or view. Syntax:

Exit-when - iterative control, EXIT-WHEN The EXIT-WHEN statement permits...

EXIT-WHEN The EXIT-WHEN statement permits a loop to complete conditionally. Whenever the EXIT statement is encountered, the condition in the WHEN clause is computed. When the co

Count operator in sql, Count Operator in SQL Example: Counting the stu...

Count Operator in SQL Example: Counting the students who have scored more than 50 in some exam (SELECT COUNT (*) FROM (SELECT DISTINCT StudentId FROM EXAM_MARK WHE

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;

Using exists - collection methods, Using EXISTS The EXISTS(n) returns ...

Using EXISTS The EXISTS(n) returns TRUE if the nth element in a collection exist. Or else, EXISTS(n) returns FALSE. Primarily, you use EXISTS with DELETE to maintain the spars

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