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".
Using a Host Variable You can declare the cursor variable in the PL/SQL host environment like an OCI or Pro C program. To use the cursor variable, you should pass it as a host
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
Obtaining a natural join by specifying the common columns Synatax: SELECT * FROM IS_CALLED JOIN IS_ENROLLED_ON USING ( StudentId ) However, a named columns join doe
Majority of Differences among 9i, 10G, 11G :- These are some combine feature which has differences among others. Automatic Workload Repository (AWR) Drop database' s
BIOCHE M ICA L ORIGIN OF LIFE - It is generally agreed by astronomers, geologists and biologists that the earth is approximately 4500-5000 million years old. It is an
IN Mode An IN parameter pass the values to the subprogram being called. Within the subprogram, an IN parameter acts like a constant. And hence, it cannot be assigned a value.
Controlling Cursor Variables You use 3 statements to control the cursor variable: OPEN-FOR, FETCH, & CLOSE. At First, you OPEN a cursor variable FOR a multi-row query. Then, y
OUT Mode An OUT parameter returns values to the caller of a subprogram. Within the subprogram, an OUT parameter act like a variable. That means that you can use an OUT formal
Row Counterparts of Table Operators SQL does not have counterparts tuple rename, tuple projection, tuple extension, tuple join and tuple compose. To obtain the same effects as
Complete the following steps to create a procedure to calculate the tax on an order. The BB_TAX table contains the states that require taxes to be submitted for Internet sales. If
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