Collection methods in pl sql, PL-SQL Programming

Collection Methods:

 The collection method is a built-in function or procedure which operates on the collections and is called using the dot notation. The methods like the COUNT, EXISTS, LIMIT, FIRST, LAST, NEXT, EXTEND, PRIOR, TRIM, & DELETE helpful to normalize the code, make collections easier to use, and make your applications easier to sustain.

The COUNT, EXISTS, LIMIT, PRIOR, FIRST, LAST, and NEXT are the functions, that appear as part of an expression. The TRIM, EXTEND, and DELETE are the procedures, that appear as a statement. The EXISTS, NEXT, PRIOR, TRIM, EXTEND, and DELETE take integer parameters.

Syntax:

 

467_collaction function in pl sql.png

Keyword and Parameter Description

collection_name:

These identify an index-by table, varray, or nested table formerly declared within the present scope.

COUNT:

The COUNT returns to the number of elements which a collection presently contains, that is helpful as the present size of a collection is not always known. You can use the COUNT wherever an integer expression is allowed.

For varrays, the COUNT always equals to LAST. For nested tables, generally, COUNT equals to LAST. But, if you delete elements from the middle of the nested table, the COUNT is smaller than LAST.

DELETE:

This procedure has 3 forms. The DELETE eliminates all the elements from a collection. The DELETE (n) eliminates the nth element from a nested table. If n is null, the DELETE (n) does nothing. The DELETE (m,n) eliminates all the elements in the range of m..n from a nested table. If m is bigger than n or if m or n is null, then DELETE (m,n) does nothing.

Index:

This is an expression which should yield an integer.

EXISTS:

The EXISTS(n) returns TRUE when the nth element in a collection exists. Or else, EXISTS(n) returns FALSE. Primarily, you can use EXISTS with DELETE to sustain the sparse nested tables. You can also use the EXISTS to avoid raising an exception whenever you reference a nonexistent element. When passed an out-of-range subscript, the EXISTS returns FALSE rather than of raising the SUBSCRIPT_OUTSIDE_LIMIT.

EXTEND:

This procedure has 3 forms. The EXTEND appends one null element to the collection. The EXTEND(n) appends n null elements to the collection. The EXTEND(n,i) appends n copies of the ith element to the  collection. The EXTEND operates on the internal size of the collection. Therefore, if EXTEND encounters deleted elements, it involves them in its tally.

FIRST, LAST:

The FIRST & LAST return the first & last (lowest limit & upper limit) index numbers in a collection. If the collection is blank, the FIRST and LAST return NULL. When the collections contain only one element, the FIRST and LAST return similar index number. For varrays, the FIRST always returns 1 and the LAST always equals to COUNT. For the nested tables, generally, LAST equals to COUNT. But, when you delete elements from the middle of the nested table, the LAST is larger than COUNT.

LIMIT:

For the nested tables, which have no maximum size, the LIMIT returns NULL. For varrays, the LIMIT returns the maximum number of elements which a varray can contain (that you should specify in its type definition).

NEXT, PRIOR:

The PRIOR(n) returns the index number which precedes an index n in a collection. The NEXT(n) returns the index number which succeed index n. If n has no predecessor, then the PRIOR(n) returns NULL. Similarly, if n has no successor, the NEXT(n) returns the NULL.

TRIM:

This procedure has 2 forms. The TRIM eliminates one element from the end of the collection. The TRIM(n) eliuminates n elements from the end of the  collection. If n is bigger than COUNT, then the TRIM(n) raises the SUBSCRIPT_BEYOND_COUNT. The TRIM operates on the internal size of a collection. Therefore, if TRIM encounters deleted elements, it involves them in its tally.

Posted Date: 10/6/2012 9:02:22 AM | Location : United States







Related Discussions:- Collection methods in pl sql, Assignment Help, Ask Question on Collection methods in pl sql, Get Answer, Expert's Help, Collection methods in pl sql Discussions

Write discussion on Collection methods in pl sql
Your posts are moderated
Related Questions
Passing Cursor Parameters You use the OPEN statement to pass the parameters to a cursor. Unless you want to accept the default values, each proper parameter in the cursor decl

This task involves developing some functions that extract data from an SQL database. The scenario is that a company which owns an online vehicle search website wants to generate so

Application to Export Excel Data to MSSQL Server table I am having a table available in excel format and features the subsequent: - Some text is in Arabic (e.g. UTF-8 encodin

Using LIMIT For nested tables, that have no maximum size, the LIMIT returns NULL. For varrays, the LIMIT returns the maximum number of elements that a varray can have (that yo

Example of UNWRAP Operator - SQL Example here shows how unwrapping can be done in longhand in SQL. Example: Unwrapping in SQL Letting CONTACT_INFO_WRAPPED denote the res

Structure of an Object Type: Similar to package, an object type has 2 parts: the specification and the body. The specification is the interface to your applications; it declar

DECLARE : This keyword signals the beginning of the declarative section of the PL/SQL block, that contains local declarations. The Items declared locally exist only within the

to write a heap sort program usin pl-sql

Procedures The procedure is a subprogram which can take parameters and be invoked. Normally, you can use a procedure to perform an action. The procedure has 2 sections: the spe

ROWID and UROWID Internally, every database table has a ROWID pseudo column that stores binary values known as rowids. Each rowid shows the storage address of a row. A physical