PL/SQL

• PL/SQL is an extension to SQL with design features of programming languages.
• Data manipulation and query statements of SQL are included with procedural units of code

PL/SQL Block Syntax and Guidelines

• Statements can continue over several lines.
• Lexical units can be separated by:
  - Spaces
  - Delimiters
  Simple Symbols
  

  Symbol	Meaning
  +	Addition operator
  -	Substraction/negation operator
  *	Multiplication operator
  /	Division operator
  = @ :	Relational operator Remote access indicator Statement terminator

  Compound Symbols

  Symbol	Meaning
  <>	Relational operator
  !=	Relational operator
  ||	Concatenation operator
  --	Single line comment
  /* */ :=	Beginning delimiter Ending comment delimiter Assignment operator

  
  - Identifiers
  - Literals
  - Comments

The UTL_HTTP package makes Hypertext Transfer Protocol (HTTP) callouts from SQL and PL/SQL. It can be used to access data on the Internet over the HTTP protocol.

The package contains a set of API that enables users to write PL/SQL programs that communicate with Web (HTTP) servers. It also contains a function that can be used in SQL queries. Besides the HTTP protocol, it also supports the HTTP protocol over the Secured Socket Layer protocol (SSL), also known as HTTPS, directly or via a HTTP proxy. Other Internet-related data-access protocols (such as the File Transfer Protocol (FTP) or the Gopher protocol) are also supported via a HTTP proxy server that supports those protocols.

When the package fetches data from a Web site using the HTTPS protocol, it requires an Oracle wallet to be set up properly by Oracle Wallet Manager. Non-HTTPS fetches do not require an Oracle wallet.

The API is divided into a number of categories. The session API manipulates configurations pertaining to the package within a database user session. The request API begins a new HTTP request, manipulates its attributes, and sends information to the Web server. The response API returns the attributes of the response and receives information the response data from the Web server. The cookies API manipulates the HTTP cookies maintained by the package within the database user session. The persistent connection API manipulates the persistent connections maintained by the package. There are also two simple functions that allow users to fetch a Web page by a single function call.