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

Group and having query, Using a join on 2 tables, select all columns and 10...

Using a join on 2 tables, select all columns and 10 rows from the 2 tables without the use of a Cartesian product. Query: SELECT * FROM EMPLOYEE1 E JOIN STAFF S ON E.EMP_

Pass the nulls to a dynamic sql, Pass the nulls to a dynamic SQL: Pas...

Pass the nulls to a dynamic SQL: Passing Nulls: Assume that you want to pass the nulls to a dynamic SQL statement. For illustration, you may write the EXECUTE IMMEDIATE

Usefulness of data type, Usefulness of Data Type In SQL, as in most c...

Usefulness of Data Type In SQL, as in most computer languages, a type can be used for constraining the values that are permitted to be used for some purpose. In particular, i

Definition of cross join - sql, Definition of CROSS JOIN - SQL Let s ...

Definition of CROSS JOIN - SQL Let s = t1 CROSS JOIN t2, where t1 and t2 are table expressions optionally accompanied by range variables. Then: Note: Here T denotes Table

Selecting objects in pl sql, Selecting Objects: Suppose that you have ...

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

Implicit cursor attributes, Implicit Cursor Attributes The Implicit cur...

Implicit Cursor Attributes The Implicit cursor attributes returns the information about the execution of an INSERT, DELETE, UPDATE, or SELECT INTO statement. The cursor attribu

Defining records, Defining and Declaring Records To create records, yo...

Defining and Declaring Records To create records, you have to define a RECORD type, and then declare records of that type. You may also define RECORD types in the declarative

Creating Views, Create a view named CustomerAddresses that shows the shippi...

Create a view named CustomerAddresses that shows the shipping and billing addresses for each customer in the MyGuitarShop database. This view should return these columns from the

Write an anonymous block that contains a pl/sql procedure, Write an anonymo...

Write an anonymous block that contains a PL/SQL procedure. The procedure takes two input parameter: oldZip and newZip, and it updates the zipcodes table by replacing all oldZip wit

Sql outer join, SQL outer join SELECT * FROM IS_CALLED NATURAL LEFT...

SQL outer join SELECT * FROM IS_CALLED NATURAL LEFT JOIN IS_ENROLLED_ON Note that adding LEFT to an invocation of CROSS JOIN has no effect unless the right-hand operand

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