PL/SQL

PL/SQL (Procedural Language/Structured Query Language) is Oracle Corporation's proprietary server-based extension to the SQL database language, and emulates the Ada programming language.

Functionality

SQL functions as a declarative language, and standard SQL - unlike some functional programming languages - does not require implementations to convert tail calls to jumps. SQL does not readily provide "first row" and "rest of table" accessors, and it cannot easily perform some constructs such as loops. PL/SQL, however, as a Turing-complete procedural language which fills in these gaps, allows Oracle database developers to interface with the underlying relational database in an imperative manner. SQL statements can make explicit in-line calls to PL/SQL functions, or can cause PL/SQL triggers to fire upon pre-defined DML events.

Programmers working in an Oracle database environment can construct PL/SQL blocks to serve as procedures, functions or in-line segments of SQL*Plus scripts. "Native Dynamic SQL" calls, in turn, allow the execution of SQL commands from within PL/SQL code.

Analogies

PL/SQL functions analogously to the embedded procedural languages associated with other relational databases. Sybase and its derivative Microsoft SQL Server have Transact-SQL, PostgreSQL has PL/PgSQL (which tries to emulate PL/SQL to an extent). Aside from some proprietary functions (notably Oracle's UTL_FILE package) PL/SQL code closely resembles Transact-SQL, allowing trivial conversion if the code does not use proprietary features.

As an alternative to (and alongside) PL/SQL, Oracle programmers can also use methods written in Java.

References

• PL/pgSQL - SQL Procedural Language
• Steven Feuerstein (2002). Oracle PL/SQL Programming, 3rd ed. O'Reilly & Associates. ISBN 0596003811.
  (Many consider this book the "bible" of PL/SQL development)
• Oracle PL/SQL FAQ