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Declaring Objects:
You can use the object types wherever built-in types like CHAR or NUMBER can be used. In the block below, you can declare object r of type Rational. Then, you can call the constructor for the object type Rational to initialize the object. The calls assign the values 6 & 8 to attributes num and den, correspondingly.
DECLARE
r Rational;
BEGIN
r := Rational(6, 8);
DBMS_OUTPUT.PUT_LINE(r.num); -- prints 6
You can declare objects as the formal parameters of the functions and procedures. In that way, you can pass objects to the stored subprograms and from one subprogram to the other. In the later illustration, you use the object type Account to specify the datatype of a formal parameter:
...
PROCEDURE open_acct (new_acct IN OUT Account) IS ...
In the illustration below, you can use object type Account to specify the return type of the function:
FUNCTION get_acct (acct_id IN INTEGER) RETURN Account IS ...
different lock modes used in the locking system
Recursion versus Iteration Dissimilar the iteration, recursion is not crucial to PL/SQL programming. Any problem which can be solved using recursion can be solving using the it
UPDATE Statement The UPDATE statement transforms the values of the specified columns in one or more rows in the table or view. Syntax:
Explicit Cursors The set of rows returned by the query can include zero, one, or multiple rows, depending on how many rows meet your search criteria. Whenever a query returns
Example of GROUPBY Operator Example: How many students sat each exam, using GROUP BY, NATURAL LEFT JOIN, and COALESCE SELECT CourseId, COALESCE (n, 0) AS n FROM COURS
Example of Foreign Key Constraint Example: Alternative formulation for 6.3 as a foreign key constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Must_be_enrolled_to_take_exam
Transaction Control The Oracle is transaction oriented; that is, Oracle uses the transactions to make sure the data integrity. The transaction is a sequence of SQL data manip
Autonomous versus Nested Transactions Though an autonomous transaction is started by the other transaction, it is not a nested transaction for the reasons shown below: (i)
Write an anonymous block that contains a PL/SQL procedure. The procedure takes two input parameter: oldZip and newZip, and it updates the zipcodes table by replacing all oldZip wit
Operators on Tables and Rows Row Extraction TUPLE FROM r, SQL has row subqueries. These are just like scalar subqueries except that they may specify more than one column.
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