Multiple assignment - sql, PL-SQL Programming

Assignment Help:

Multiple Assignment- SQL

SQL supports multiple assignment to local variables and also applies multiple assignment semantics in SET clauses of UPDATE statements, but does not support multiple assignment in connection with updates on table targets. Thus, SQL has no counterpart to the theory book's Example, simultaneously deleting from both COURSE and IS_ENROLLED_ON. If we assume that there must be at least one enrolment for each course, and that students can enroll only on existing courses, deferred constraint checking has to be used, as shown in Example here.

Example: Withdrawing course C3 and deleting any enrolments on C3

Assume the definition of IS_ENROLLED_ON includes

CONSTRAINT Course_must_exist_for_enrolment

FOREIGN KEY (CourseId) REFERENCES COURSE ON DELETE NO ACTION

and the definition of COURSE includes

CONSTRAINT Enrolment_must_exist_for_course

CHECK ( CourseId IN (SELECT CourseId FROM IS_ENROLLED_ON)


Related Discussions:- Multiple assignment - sql

Using forall statement - bulk bind performance improvement, Using the FORAL...

Using the FORALL Statement The keyword FORALL instruct the PL/SQL engine to bulk-bind input collections before sending them all to the SQL engine. Though the FORALL statement

Collection methods in pl sql, Collection Methods:   The collection me...

Collection Methods:   The collection method is a built-in function or procedure which operates on the collections and is called using the dot notation. The methods like the C

How to use the explain plan for statement, Using the student and faculty ta...

Using the student and faculty tables create a select query that outputs all students for a specific advisor. Generate the execution plan, select out the explain plan . Create an

Theory of biogenesis, THEORY OF BIOGENESIS - This theory explains th...

THEORY OF BIOGENESIS - This theory explains that the existing living organisms originated from pre-existing living beings not from non living entities. This concept of or

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

Parameter and keyword description - fetch statement, Parameter and Keyword ...

Parameter and Keyword Description: cursor_name: This identifies an explicit cursor formerly declared within the present scope. cursor_variable_name: These identif

Exception handling, Exception handling In the PL/SQL, a warning or erro...

Exception handling In the PL/SQL, a warning or error condition is known as an exception. The Exceptions can be internally defined (by the run-time system) or user defined. The

Parameter and keyword description - exit statement, Parameter and Keyword D...

Parameter and Keyword Description: EXIT: An unconditional EXIT statement (i.e., one without a WHEN clause) exits the present loop instantly. The Execution resumes with th

Opening a cursor, Opening a Cursor Opening the cursor executes the que...

Opening a Cursor Opening the cursor executes the query & identifies the result set that consists of all rows that meet the query search criteria. For the cursors declared usin

Oracle, Literature review

Literature review

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