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!
WHEN or THEN Key Constraints
Suppose a table has two columns representing a period of time throughout which the information conveyed by the other columns is recorded as having been the case. A salary history table for employees, with columns From and To for dates defining the applicable time periods, would be a good example.
A constraint is needed to avoid the possibility of an employee being shown as having two different salaries on the same day, which could happen if two rows for the same employee have overlapping periods indicated by their From and To dates. The term "WHEN/THEN constraint" appeals to the notion of "unpacking" the table so that each row is replaced by one or more rows, one for each date contained in its from-to period: when the relation is unpacked, then the given key constraint (e.g., on employee number and date) is to hold.
Fetching with a Cursor The FETCH statements retrieve the rows in the result set one at a time. After each and every fetch, the cursor advance to the next row in the result set
What Is a Package? The package is a schema object that group logically related PL/SQL items, types, and subprograms. The Packages usually have 2 parts, a specification & a bo
Using FIRST and LAST FIRST and LAST return the first and last (minimum and maximum) index numbers in a collection. When the collection is empty, the FIRST and LAST return NULL
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
Scope and Visibility The References to an identifier are resolved according to its visibility and scope. The scope of an identifier is that area of a program unit (subprogram, b
Using a join on 2 tables, select all columns and 10 rows from the 2 tables without the use of a Cartesian product. Query: SELECT * FROM EMPLOYEE1 E JOIN STAFF S ON E.EMP_
Indeterminacy in SQL Some SQL expressions are actually not function invocations at all in the mathematical sense, being indeterminate-invocations operating on identical input
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
ROWID The ROWID returns the rowid (binary address) of a row in the database table. You can use the variables of the type UROWID to store rowids in a readable format. In the il
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
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