Manipulating objects in pl sql, PL-SQL Programming

Assignment Help:

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 statements to insert an object, call its methods, select its attributes, & update its state.

In the SQL*Plus script shown below, the INSERT statement calls the constructor for the object type Rational, and then inserts the resultant object. The SELECT statements retrieve the value of the attribute num. The UPDATE declaration calls member method reciprocal, that returns a Rational value after exchanging the attributes num and den. Note that the table alias is needed whenever you reference an attribute or method.

CREATE TABLE numbers (rn Rational, ...)

/

INSERT INTO numbers (rn) VALUES (Rational(3, 62)) -- inserts 3/62

/

SELECT n.rn.num INTO my_num FROM numbers n ... -- returns 3

/

UPDATE numbers n SET n.rn = n.rn.reciprocal ... -- yields 62/3

/

When you instantiate an object in this way, it has no individuality outside the database table. Though, the object type exists separately of any table, and can be used to create objects in the other ways.

In the later illustration, you build a table which stores objects of the type Rational in its rows. These tables, having rows of objects, are known as the object tables. Each column in a row corresponds to the attribute of the object type. The Rows can have various column values.

CREATE TABLE rational_nums OF Rational;

Each row in the object table has an object identifier that uniquely identifies the object stored in that row and serve as a reference to the object.


Related Discussions:- Manipulating objects in pl sql

What is a record, What Is a Record  ? A record is a group of related...

What Is a Record  ? A record is a group of related data items that stored in the fields, each with its own name and datatype. Assume that you have different data about an em

Calculate the total shopper spending, Many of the reports generated from th...

Many of the reports generated from the system calculate the total dollars in purchases for a shopper. Complete the following steps to create a function named TOT_PURCH_SF that acce

Join and and in sql, JOIN and AND in SQL In this Section is all about ...

JOIN and AND in SQL In this Section is all about one operator, JOIN. SQL's closest counterpart, NATURAL JOIN, has already been covered. Here we look at several other "join" op

Currval and nextval - sql pseudocolumns, CURRVAL and NEXTVAL The serie...

CURRVAL and NEXTVAL The series is a schema object which generates the sequential numbers. Whenever you form a sequence, you can specify its primary value and an increment. T

Sql is a database language, SQL Is a Database Language: The commands g...

SQL Is a Database Language: The commands given to a DBMS by an application are written in the database language of the DBMS. The term data sublanguage is sometimes used instea

Cursor variables, What Are Cursor Variables  ? The Cursor variables ar...

What Are Cursor Variables  ? The Cursor variables are like C or Pascal pointers that hold the memory location (address) of some item rather of the item itself. Therefore, decl

Interesting properties of cross join - sql, Interesting properties of CROSS...

Interesting properties of CROSS JOIN - SQL Compare these with the "interesting properties of JOIN", CROSS JOIN is associative but not commutative. Unlike JOIN and NATURAL JOI

Goto statement - syntax, GOTO Statement   The GOTO statement branches ...

GOTO Statement   The GOTO statement branches categorically to a block label or statement label. The label should be exclusive within its scope and should precede a PL/SQL bloc

Use of count in sql, Use of COUNT in SQL It describes and discusses va...

Use of COUNT in SQL It describes and discusses various general methods of expressing constraints, eventually noting that support for "=" with relation operands is sufficient f

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd