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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 ...
%ISOPEN The %ISOPEN yields TRUE if its cursor or cursor variable is open; or else, the %ISOPEN yields FALSE. In the illustration, you use the %ISOPEN to select an action:
ROWNUM The ROWNUM returns a number representing the order in which a row was selected from the table. The first row selected has a ROWNUM of 1; the second row has a ROWNUM of
Table Literals - SQL One might expect SQL to support table literals in the manner illustrated in Example 2.2, but in fact that is not a legal SQL expression. Example: Not a
IN Operator The operator IN tests the set membership. This means "equal to any member of." The set may have nulls, but they are ignored. For illustration, the statement below do
Using EXTEND To enlarge the size of a collection, use EXTEND. This process has 3 forms. The EXTEND appends one null element to a collection. And the EXTEND(n) appends n null e
Expression: This is a randomly complex combination of constants, variables, literals, operators, & function calls. The simplest expression consists of a single variable. If th
Use External Routines The PL/SQL is particular for the SQL transaction processing. Therefore, several tasks are more quickly completed in a lower-level language like C that is
Overloading The PL/SQL overloads the subprogram names. That is, you can use similar name for few different subprograms as long as their formal parameters differ in the number
Using Operator REF: You can retrieve refs by using the operator REF that, like VALUE, takes as its argument a correlation variable. In the illustration below, you retrieve one
MERGE and TRUNCATE in SQL SQL has two more table update operators, MERGE and TRUNCATE. MERGE, like INSERT, takes a source table s and uses it to update a target table t. Brief
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