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!
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)
Manipulating Objects: You can use an object type in the CREATE TABLE statement to indicate the datatype of a column. When the table is created once, you can use the SQL statem
Logical Operators The logical operators AND, NOT, and OR follow the tri-state logic shown in table below. The AND and OR are binary operators; NOT is a unary operator.
Using SET TRANSACTION You use the SET TRANSACTION statement to begin the read-only or read-write transaction, start an isolation level, or assign your present transaction to a
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
Loop Labels Like the PL/SQL blocks, loops can also be labeled. The label, an undeclared identifier enclosed by double angle brackets, should appear at the beginning of the LOOP
Example of COALESCE operator Example: Give the total of marks for each exam (simplified solution) SELECT CourseId, COALESCE ((SELECT SUM (Mark) FROM EXAM_MARK AS EM
Use Bulk Binds If SQL statements execute inside a loop using the collection elements as bind variables, context switching between the PL/SQL & SQL engines can slow down the ex
%ISOPEN The Oracle closes the SQL cursor automatically after executing its related SQL statement. As a result, the %ISOPEN forever yields FALSE.
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
Components of an Object Type: An object type encapsulates the operations and data. Therefore, you can declare the methods and attributes in an object type specification, but no
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