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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 ...
Defining REF CURSOR Types To make cursor variables, you take 2 steps. At first, you define a REF CURSOR type, and then declare the cursor variables of that type. You can defin
Using Aliases The Select-list items fetched from a cursor related with the %ROWTYPE should have simple names or, if they are expressions, should have aliases. In the example bel
Example of Alternative formulation as a table constraint Example: Alternative formulation as a table constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Must_be_enrolled_to_
a. Create a table odetails_new. It has all the attributes of odetails and an additional column called cost, whose values are the product of the quantity and price of the part bein
Data Types in SQL SQL's concept does not differ significantly from that defined in the theory book, apart from that business concerning NULL. However, the theory book equates
INSERT Statement The INSERT statement adds fresh rows of data to the specified database table or view. Syntax:
DELETE Statement The DELETE statement eliminates whole rows of data from the specified table or view. Syntax:
Semijoin and Composition - SQL For semijoin, the dyadic relational operator MATCHING, defined thus: r1 MATCHING r2, where r1 and r2 are relations such that r1 JOIN r2 is de
help
Effects of NULL for Table Expression Here's an important distinction between expressions denoting tables and expressions denoting multisets of rows: a table expression cannot
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