Advanced Oracle PL/SQL Programming with Packages

Chapter 6. PLV: Top-Level Constants and Functions

Let's start our exploration into PL/Vision with the PLV package, which can be considered the lowest-level package or perhaps even the "miscellaneous" package. It provides a single collection point for constants and basic functions used throughout PL/Vision. Whenever I thought of something useful that was needed in more than one package but that did not belong in any particular functional package, it ended up in PLV.

The PLV (PL/Vision) package offers the following:

• A NULL substitution value. You can set in PLV the string you want to use in place of NULL for display purposes.

• A product-wide date mask. You can set a date mask that will be used throughout PL/Vision when converting and displaying dates. You can also use this mask yourself in SQL and PL/SQL.

• A set of assertion routines. These programs help you construct more robust applications by letting you easily verify assumptions.

• Miscellaneous utilities. You can obtain the current date and time, pause your PL/SQL program, obtain the error message for an Oracle error number, and more.

• A set of constants used throughout PL/Vision. These named constants help users of PL/Vision (and packages within PL/Vision) avoid hard-coding literals.

• Predefined datatypes. PL/Vision uses these datatypes as anchors (with the %TYPE declaration attribute) for declaring other variables. You might use them, too, or you might simply follow the example in your own applications.

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