Using first and last - collection method, PL-SQL Programming

Using FIRST and LAST

FIRST and LAST return the first and last (minimum and maximum) index numbers in a collection. When the collection is empty, the FIRST and LAST return NULL. If the collections contains only one element, the FIRST and LAST return the same index number, as the example below shows:

IF courses.FIRST = courses.LAST THEN ... -- only one element

The later example shows that you can use FIRST and LAST to specify the lower and upper bounds of a loop range provided each element in that range exists:

FOR i IN courses.FIRST..courses.LAST LOOP ...

However, you can use the FIRST or LAST where the integer expression is allowed. In the example below, you use FIRST to initialize the loop counter:

i := courses.FIRST;

WHILE i IS NOT NULL LOOP...

For varrays, the FIRST always returns 1 and LAST always equals to COUNT. For the nested tables, FIRST generally returns 1. But, if you delete elements from the beginning of the nested table, FIRST returns a number bigger than 1. Also for the nested tables, the LAST generally equals to COUNT. But, if you delete elements from the middle of a nested table, the LAST becomes larger than COUNT.

Posted Date: 10/4/2012 3:15:27 AM | Location : United States







Related Discussions:- Using first and last - collection method, Assignment Help, Ask Question on Using first and last - collection method, Get Answer, Expert's Help, Using first and last - collection method Discussions

Write discussion on Using first and last - collection method
Your posts are moderated
Related Questions
Comparison Operators The Comparison operators can compare one expression to another. The outcome is always true, false, or null. Usually, you use a comparison operators in condi

%ROWCOUNT When its cursor or cursor variable is opened, the %ROWCOUNT is zeroed. Before the first fetch, the %ROWCOUNT yields 0. Afterward, it yields the number of rows fetche

IS NULL Operator The IS NULL operator returns the Boolean value TRUE whenever its operand is null or FALSE if it is not null. The comparisons including the nulls always yield NU

Define basic operators of relational algebra with an example each

Creating a SQL file 1. Open a new file in Notepad++ and save it to the location c:\mysql\bin, with the name lab8script.sql (the file extension should be .sql ). Add a MySQL co

Main features of PL/SQL A good way to get familiar with PL/SQL is to look at a sample program. The below program processes an order for tennis rackets. At first, it declares a

%ISOPEN The %ISOPEN yields TRUE if its cursor or cursor variable is open; or else, the %ISOPEN yields FALSE. In the illustration, you use the %ISOPEN to select an action:

MERGE and TRUNCATE in SQL SQL has two more table update operators, MERGE and TRUNCATE. MERGE, like INSERT, takes a source table s and uses it to update a target table t. Brief

Oracle 10G new features:- Automatic Database Diagnostic Monitor System Advancements - these methods will provides several methods for extracting reports through the Automatic

Scoping Within the similar scope, all the declared identifiers should be unique. So, even if their datatypes differ, the variables and parameters cannot share the similar name.