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Advanced Oracle PL/SQL Programming with Packages

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8. PLVtab: Easy Access to PL/SQL Tables

The PLVtab (PL/Vision TABle) packag e offers predefined PL/SQL table types and programs to make it easier to declare, use, and display the contents of PL/SQL tables. PL/SQL tables are the closest things to arrays in PL/SQL , but there are a number of complications. First, to use a PL/SQL table, you first have to declare a table type. Then you can declare and use the PL/SQL table itself. Beyond the definition of the PL/SQL table, the fact that it is a sparse, unbounded, homogeneous data structure can lead to complications, particularly when it comes to scanning and displaying those structures (see Chapter 10 of Oracle PL/SQL Programming ).

By using PLVtab, you can avoid (in most cases) having to define your own PL/SQL table types. You can also take advantage of flexible, powerful display procedures to view table contents.

When you display the contents of PL/SQL tables, PLVtab allows you to:

  • Show or suppress a header for the table

  • Show or suppress the row numbers for the table values

  • Display a prefix before each row of the table

This chapter shows how to use the different aspects of PLVtab.

8.1 Using PLVtab-Based PL/SQL Table Types

When you use PL/SQL tables, you normally perform a number of common actions, including defining the table type, declaring the table, filling up the rows, referencing the rows, and emptying the table when done. When using a PLVtab-based table, you do not have to declare the table type. Instead you simply reference the package-based type in your declaration. PLVtab predefines the following PL/SQL table TYPEs, shown in Table 8.1 :


Table 8.1: Table Types Predefined in PLVtab

Type

Description

boolean_table

PL/SQL table of Booleans

date_table

PL/SQL table of dates

integer_table

PL/SQL table of integers

number_table

PL/SQL table of numbers

vc30_table

PL/SQL table of VARCHAR2(30) strings

vc60_table

PL/SQL table of VARCHAR2(60) strings

vc80_table

PL/SQL table of VARCHAR2(80) strings

vc2000_table

PL/SQL table of VARCHAR2(2000) strings

ident_table

PL/SQL table of VARCHAR2(100) strings; matches PLV.plsql_identifier declaration.

vcmax_table

PL/SQL table of VARCHAR2(32767) strings

Let's compare the "native" and PL/Vision approaches to defining PL/SQL tables. In the following anonymous block, I define a PL/SQL table of Booleans without the assistance of PLVtab .

DECLARE
   TYPE bool_tabtype IS TABLE OF BOOLEAN
      INDEX BY BINARY_INTEGER;
   yesno_tab bool_tabtype;
BEGIN

With the PLVtab package in place, all I have to is the following:

DECLARE
   yesno_tab PLVtab.boolean_table;
BEGIN

Once you have declared a table using PLVtab, you manipulate that table as you would a table based on your own table TYPE statement.


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