Data abstraction, PL-SQL Programming

Assignment Help:

Data Abstraction

The Data abstraction extracts the important properties of data while ignoring the not necessary details. Once you design a data structure, you can fail to remember the details and focus on designing algorithms that manipulate the data structure.

Collections

The collection types TABLE and VARRAY permit you to declare nested tables and variable-size arrays (varrays in short). A collection is an ordered group of elements, all of the similar type. Every element has a unique subscript that determines its place in the collection.

To reference an element, use the standard subscripting syntax. For e.g., the following call references the 5th element in the nested table returned by the function new_hires:

DECLARE

TYPE Staff IS TABLE OF Employee;

staffer Employee;

FUNCTION new_hires (hiredate DATE) RETURN Staff IS

BEGIN ... END;

BEGIN

staffer := new_hires('10-NOV-98')(5);

...

END;

The Collections work like an array found in most third-generation programming languages. The collections can also be passed as parameters. And hence, you can use them to move columns of data into and out of database tables or between the client-side applications and stored subprograms.

Records

You can use the %ROWTYPE attribute to declare a record that shows a row in a table or a row fetched from a cursor. Although, with a user-defined record, you can declare fields of your own. The Records contain exclusively named fields that can have different datatypes. Assume that you have different data about an employee like name, salary, & hire date. These items are not similar in type but logically related. Records containing a field for each item treat the data as a logical unit. Consider the example shown below:

DECLARE

TYPE TimeRec IS RECORD (hours SMALLINT, minutes SMALLINT);

TYPE MeetingTyp IS RECORD

(

date_held DATE,

duration TimeRec, -- nested record

location VARCHAR2(20),

purpose VARCHAR2(50));

Remember that you can nest the records. That is, the record can be the component of another record.


Related Discussions:- Data abstraction

Declaring objects in pl/sql, Declaring Objects: You can use the object ...

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, yo

Maintain an audit trail of product table changes, The accuracy of product t...

The accuracy of product table data is critical and the Brwebean's. owner wants to have an audit file that contains information regarding all DML activity on the BB_PRODUCT table. T

Union without corresponding - sql, UNION without CORRESPONDING - SQL T...

UNION without CORRESPONDING - SQL The use of UNION without CORRESPONDING. Example is merely by omitting CORRESPONDING, but only because the operands have identical SELECT clau

Expression in assignment statement - pl sql, Expression: This is a ran...

Expression: This is a randomly complex combination of constants, variables, literals, operators, & function calls. The simplest expression consists of a single variable. If th

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

Best practices/Data Warhousing, What are 3 good practices of modeling and/o...

What are 3 good practices of modeling and/or implementing data warehouses?

%found - explicit cursor attributes, %FOUND Subsequent to a cursor or ...

%FOUND Subsequent to a cursor or cursor variable is opened but before the first fetch, the %FOUND yields NULL. Afterward, it yields TRUE when the last fetch returned a row, or

Exception handling, set serveroutput on declare a number(5); b n...

set serveroutput on declare a number(5); b number(5); c number(5); begin a:=&a; b:=&b; c:=a/b; dbms_output.put_line(c); exception when zero_d

Expressions - syntax, Expressions   An expression is a randomly comple...

Expressions   An expression is a randomly complex combination of the constants, variables, literals, operators, & function calls. The simplest expression is the single variabl

Advantages of packages, Advantages of Packages The benefits of the Pack...

Advantages of Packages The benefits of the Packages are as shown below: Modularity The Packages encapsulate logically associated items, types, and subprograms in the

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