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.
Use the PLS_INTEGER Datatype When you require to declare an integer variable, use the datatype PLS_INTEGER that is the most efficient numeric type. That is as the PLS_INTEGER
"Not Enforced" Table Constraints A constraint that is not enforced is not really a constraint within the meaning of the act, but SQL does have such a concept and it needs to b
%ROWCOUNT When its cursor or cursor variable is opened, the %ROWCOUNT is zeroed. Before the first fetch, the %ROWCOUNT yields 0. Afterward, it yields the number of rows fetche
%NOTFOUND The %NOTFOUND is the logical opposite of the %FOUND. The %NOTFOUND yields TRUE when an INSERT, UPDATE, or DELETE statement affected no rows, or the SELECT INTO state
Object Type: The object type is a user-defined composite datatype which encapsulates a data structure along with the functions and procedures required to manipulate the data
Assignment Statement: The assignment statement sets the present value of the variable, parameter, field, or element. The statement consists of an assignment target followed by
Use of Table Comparisons - SQL Table comparisons where it is noted that although table expressions cannot be compared, we have TABLE (t) to convert a table expression t into
What Is a Collection The collection is an ordered group of elements, all of similar type (for e.g. the grades for a class of students). Each element has a unique subscript whic
Overriding Default Locking By default, the Oracle locks the data structures for you automatically. Though, you can request exact data locks on rows or tables when it is to you
Datatypes Every constant and variable has a datatype that specifies the storage format, constraints, and the valid range of values. The PL/SQL gives a variety of predefined dat
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