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

Understanding nested tables, Understanding Nested Tables Within the data...

Understanding Nested Tables Within the database, the nested tables can be considered as one-column database tables. The Oracle stores the rows of a nested table in no specific o

Interesting properties of cross join - sql, Interesting properties of CROSS...

Interesting properties of CROSS JOIN - SQL Compare these with the "interesting properties of JOIN", CROSS JOIN is associative but not commutative. Unlike JOIN and NATURAL JOI

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

Projection and existential quantification - sql, Projection and Existential...

Projection and Existential Quantification - SQL Intuitively it might seem that projection in SQL is simply a matter of specifying the required columns in the SELECT clause, a

Recursive subprograms, Recursive Subprograms The recursive subprogram ...

Recursive Subprograms The recursive subprogram is the one that calls itself. Think of a recursive call as a call to a few other subprograms that does the similar task as your

Closing a cursor - explicit cursor, Closing a Cursor The CLOSE stateme...

Closing a Cursor The CLOSE statements disable the cursor, and the result set becomes undefined. An illustration of the CLOSE statement as shown: CLOSE c1;

Overloading, Overloading The PL/SQL overloads the subprogram names. T...

Overloading The PL/SQL overloads the subprogram names. That is, you can use similar name for few different subprograms as long as their formal parameters differ in the number

Homework, What are the rates for help in writing PL/SQL procedures and func...

What are the rates for help in writing PL/SQL procedures and functions?

Sql scripts, The SQL ‘CREATE TABLE' scripts for all the tables you have imp...

The SQL ‘CREATE TABLE' scripts for all the tables you have implemented. Note that your tables must correspond exactly to the ERD you have provided in 1. above, or you will lose ma

Truth tables , Truth Tables: However in propositional logic - here we ...

Truth Tables: However in propositional logic - here we are restricted to expressing sentences and where the propositions are true or false - so we can check where a particular

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