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

Example of when or then constraints - sql, Example of WHEN or THEN Constrai...

Example of WHEN or THEN Constraints A concrete example showing how SQL supports WHEN/THEN constraints CREATE TABLE SAL_HISTORY (EmpNo CHAR (6), Salary INTEGER NOT NULL,

Cursor attributes in pl sql, Cursor Attributes   The Cursors and curso...

Cursor Attributes   The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:

How exceptions propagate in pl/sql programming?, How Exceptions Propagate ?...

How Exceptions Propagate ? Whenever an exception is raised, and if the PL/SQL cannot find a handler for it in the present subprogram or block, the exception propagates. That is

Conditionals - sql, Conditionals - SQL At first sight SQL does not app...

Conditionals - SQL At first sight SQL does not appear to have a single operator for expressing logical implication. In this respect it would be in common with most programming

Scope and visibility- pl/sql, Scope and Visibility The References to an ...

Scope and Visibility The References to an identifier are resolved according to its visibility and scope. The scope of an identifier is that area of a program unit (subprogram, b

Control structure, Control Structures The Control structures are the mo...

Control Structures The Control structures are the most important PL/SQL extension to the SQL. Not only does PL/SQL let you manipulate Oracle data, it lets you process the data

Keyword and parameter description - delete statement, Keyword and Parameter...

Keyword and Parameter Description: table_reference: This specifies a table or view that should be accessible when you execute the DELETE statement, and for that you must

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

Defining autonomous transactions, Defining Autonomous Transactions To ...

Defining Autonomous Transactions To define an autonomous transaction, you use the pragma (compiler directive) AUTONOMOUS_TRANSACTION. The pragma instructs the PL/SQL compiler

Example of groupby operator - sql, Example of GROUPBY Operator Example...

Example of GROUPBY Operator Example: How many students sat each exam, using GROUP BY, NATURAL LEFT JOIN, and COALESCE SELECT CourseId, COALESCE (n, 0) AS n FROM COURS

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