Effect of anonymous columns, PL-SQL Programming

Assignment Help:

Effect of Anonymous Columns

Now, recall that a VALUES expression denotes a table with undefined column names. If an initial value is to be specified when a base table is created, column definitions have to be implied by that initial value, so the question arises, how can a VALUES expression provide the initial value for a base table? The answer is that you have to learn an extra syntactic construct for that purpose, shown in Example.

Example: Specifying an initial value for a base table.

CREATE TABLE ENROLMENT (StudentId, Name, CourseId)

AS (VALUES (SID ('S1'), 'Anne', CID ('C1')),

(SID ('S2'), 'Boris', CID ('C1')))

WITH DATA;

Explanation:

  1. (StudentId, Name, CourseId) provides the names, positionally corresponding to the anonymous columns of the AS table.
  2. WITH DATA specifies that the given table is indeed to be the initial value. Curiously, this is required, unless WITHOUT DATA is written instead, in which case the AS table serves only to determine the declared types of the columns of the base table.
  3. SQL does not allow constraints to be declared if AS is used in place of explicit column definitions.

Related Discussions:- Effect of anonymous columns

Semijoin and composition - sql, Semijoin and Composition - SQL For sem...

Semijoin and Composition - SQL For semijoin, the dyadic relational operator MATCHING, defined thus: r1 MATCHING r2, where r1 and r2 are relations such that r1 JOIN r2 is de

Rephrase conditional control statements, Rephrase Conditional Control State...

Rephrase Conditional Control Statements When computing a logical expression, the PL/SQL uses short-circuit evaluation. That is, the PL/SQL stops evaluating the expression as s

Update command- sql, UPDATE Command- SQL Loosely speaking, UPDATE chan...

UPDATE Command- SQL Loosely speaking, UPDATE changes some of the column values of some existing rows of its target table. Thus, although some rows disappear from the target an

Restriction and and - sql, Restriction and AND - SQL Restriction is av...

Restriction and AND - SQL Restriction is available via the WHERE operator, and so it is in SQL. However, by Example showing how a certain simple restriction can be expressed u

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

Recursion, Recursion The Recursion is a powerful method for simplify th...

Recursion The Recursion is a powerful method for simplify the design of the algorithms. Principally, the recursion means the self-reference. In the recursive mathematical serie

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

If statement - syntax, IF Statement The IF statement executes a series ...

IF Statement The IF statement executes a series of statement conditionally. Whether the series is executed or not depends on the value of the Boolean expression. Syntax:

Calculate the number of tuples, Question: (a) The objective of query opti...

Question: (a) The objective of query optimization is to choose the most efficient strategy for implementing a given relational query, thereby improving the system performance. On

Named notation, Named Notation The second procedure call uses the name...

Named Notation The second procedure call uses the named notation. An arrow (=>) serve as the relationship operator that associates the formal parameter to the left of the arro

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