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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 ...
WHILE-LOOP The WHILE-LOOP statement relates a condition with the series of statements enclosed by the keywords LOOP and END LOOP, as shown: WHILE condition LOOP sequence_of_sta
EXIT Statement You can use the EXIT statement to exit a loop. The EXIT statement has 2 forms: the conditional EXIT WHEN and the unconditional EXIT. With the either form, you
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
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
Use of Table Expressions - Expressing Constraint Conditions With the exception of key constraints, the examples in the theory book all explicitly reference at least one relvar
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
What Are Subprograms? The Subprograms are named PL/SQL blocks which can take parameters and be invoked. The PL/SQL has 2 types of subprograms known as the procedure s and func
Closing a Cursor The CLOSE statements disable the cursor, and the result set becomes undefined. An illustration of the CLOSE statement as shown: CLOSE c1;
Selecting Objects: Suppose that you have run the SQL*Plus script below that creates object type Person and object table persons, and that you have settled the table: CREATE
Renaming Columns - SQL SQL has no direct counterpart of RENAME. To derive the table on the right in Figure 4.4 from the table on the left, Tutorial D has IS_CALLED RENAME ( St
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