Oracle PL/SQL Programming, Third Edition

The PRAGMA Keyword

The PRAGMA keyword is used to signify that the remainder of the PL/SQL statement is a pragma, or directive, to the compiler. Also called apseudoinstruction, a pragma simply passes information to the compiler rather than getting transformed into a particular execution.

The syntax for using the PRAGMA keyword is as follows:

PRAGMA instruction;

where instruction is a statement providing instructions to the compiler. The PL/SQL compiler will accept such directives anywhere in the declaration section.

PL/SQL offers the following pragmas:

AUTONOMOUS_TRANSACTION

Tells the PL/SQL runtime engine to commit or roll back any changes made to the database inside the current block without affecting the main or outer transaction. See Chapter 13 for more information. Introduced in Oracle8i.

EXCEPTION_INIT

Tells the compiler to associate a particular error number with an identifier you have declared as an exception in your program. See Chapter 6 for more information.

RESTRICT_REFERENCES

Tells the compiler the purity level (freedom from side effects) of a packaged program. See Chapter 16 for more information.

SERIALLY_REUSABLE

Tells the PL/SQL runtime engine that package-level data should not persist between references to that data. See Chapter 17 for more information. Introduced in Oracle8.

The following block demonstrates the use of the EXCEPTION_INIT pragma to name a built-in exception that would otherwise have only a number.

DECLARE no_such_sequence EXCEPTION; PRAGMA EXCEPTION_INIT ...