PL/SQL
PL/SQL (Procedural Language/Structured Query Language) is Oracle Corporation's procedural extension language for SQL and the Oracle relational database. PL/SQL's general syntax resembles that of Ada or Pascal.
PL/SQL is one of three key programming languages embedded in the Oracle Database, along with SQL itself and Java.
PL/SQL is available in Oracle Database (since version 7), TimesTen in-memory database (since version 11.2.1), and IBM DB2 (since version 9.7).
PL/SQL supports variables, conditions, loops and exceptions. Arrays are also supported, though in a somewhat unusual way, involving the use of PL/SQL collections. PL/SQL collections are a slightly advanced topic.
Implementations from version 8 of Oracle Database onwards have included features associated with object-orientation.
PL/SQL program units (essentially code containers) can be compiled into the Oracle database. Programmers can thus embed PL/SQL units of functionality into the database directly. They also can write scripts containing PL/SQL program units that can be read into the database using the Oracle SQL*Plus tool.
Once the program units have been stored into the database, they become available for execution at a later time.
While programmers can readily embed Data Manipulation Language (DML) statements directly into their PL/SQL code using straight forward SQL statements, Data Definition Language (DDL) requires more complex "Dynamic SQL" statements to be written in the PL/SQL code. However, DML statements underpin the majority of PL/SQL code in typical software applications.
In the case of PL/SQL dynamic SQL, early versions of the Oracle Database required the use of a complicated Oracle DBMS_SQL package library. More recent versions have however introduced a simpler "Native Dynamic SQL", along with an associated EXECUTE IMMEDIATE syntax.
Oracle Corporation customarily extends package functionality with each successive release of the Oracle Database.
Sources
Wikipedia contributors. "PL/SQL." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 5 Sep. 2011. Web. 12 Sep. 2011.