Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Procedural Constraint Enforcement (Triggers)
SQL has an alternative method of addressing database integrity, involving event-driven procedural code. The special procedures that can be used for this purpose are called triggers and the events that activate them are specified update operations. For example, suppose it is required for every row in IS_CALLED to have a matching row on StudentId in IS_ENROLLED_ON, enforcing a business rule to the effect that every registered student must be enrolled on at least one course. Then a triggered procedure might be activated every time INSERT is used to add a row to IS_CALLED, checking to see if a matching row exists in IS_ENROLLED_ON and raising an exception if there isn't one. But that wouldn't be sufficient to address the requirement.
Further triggers would be needed, activated by UPDATE statements on IS_CALLED and IS_ENROLLED_ON that cause changes to StudentId values in either of those tables, and by DELETE statements on IS_ENROLLED_ON. As this simple example demonstrates, use of triggered procedures for constraint enforcement can be complicated and error-prone. As one practitioner told me, "It quickly gets so complicated that it's almost impossible for a human not to make errors..., and even when you're not facing a 'complicated' case, the work to be done is tedious and boring".
Fetching from a Cursor Variable The FETCH statement retrieve rows one at a time from the product set of a multi-row query. The syntax for the same is as shown: FETCH {curso
Using PRIOR and NEXT The PRIOR(n) returns the index number that precede index n in a collection. The NEXT(n) returns the index number which succeed the index n. If n has no pr
Demonstrate your knowledge of PL/SQL programming by writing and thoroughly testing triggers and stored procedures associated with an e-commerce application that provides security l
Consider the schema for FreeChecking Bank, that we designed given below. Translate the given ER schema into SQL CREATE TABLE statements (indicating primary key, unique and foreign
Declaring Exceptions The Exceptions can be declared only in the declarative part of the PL/SQL subprogram, block, or package. By introducing its name, you can declare an excep
Assignment of Variable - Updating a Variable Syntax: SET SN = SID ('S2'); This can obviously be read as "set the variable SN to be equal in value to SID ( 'S2' )".
Semidifference via EXCEPT and JOIN - SQL SELECT * FROM (SELECT StudentId FROM IS_CALLED WHERE Name = 'Devinder' EXCEPT DISTINCT CORRESPONDING SELECT StudentId
Read-Only Operator (+) - SQL The term read-only operator to the mathematical term function. Here I just need to add that the SQL standard reserves the term function for read-
Write a pl/sql block that declares and uses cursors with parameters. In a loop, use a cursor to retrieve the department number and the department name from the departments table
At times, Brewbean's has changed the id number for existing products. In the past, they have had to add a new product row with the new id to the BB_PRODUCT table, modify all the co
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd