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A procedure may also be created in a PL/SQL package - this is called a Package Procedure. A procedure created in a PL/SQL anonymous block is called a nested procedure. The standalone or package procedures, stored in the database, are referred to as "stored procedures". Procedures can have three types of parameters: IN, OUT and IN OUT.
Major DBMSs, including SQLite, [5] MySQL, [6] Oracle, [7] IBM Db2, [8] Microsoft SQL Server [9] and PostgreSQL [10] support prepared statements. Prepared statements are normally executed through a non-SQL binary protocol for efficiency and protection from SQL injection, but with some DBMSs such as MySQL prepared statements are also available using a SQL syntax for debugging purposes.
In many systems, stored procedures can be granted access rights to the database that users who execute those procedures do not directly have. Some protection from SQL injection attacks Stored procedures can be used to protect against injection attacks. Stored procedure parameters will be treated as data even if an attacker inserts SQL commands.
PreparedStatement allows the dynamic query to vary depending on the query parameter. [11] CallableStatement – CallableStatement is a subinterface of the Statement interface. [11] It is used for executing stored procedures on the database. [11] [12] Both input and output parameters must be passed into the database for stored procedures. [13]
When used in the context of a class, a procedure is a method. [27] Each parameter has a data type that can be specified, but if not, defaults to Object for later versions based on .NET and variant for VB6. [28] VB supports parameter passing conventions by value and by reference via the keywords ByVal and ByRef, respectively.
Oracle Forms 3 was the first version to allow PL/SQL to be used within Forms triggers and procedures/SQL Functions could also be used as an undocumented feature. Forms 3 was a character mode application and was primarily used in terminals such as Digital VT220 and PCs running Microsoft DOS.
In computing, a procedural parameter is a parameter of a procedure that is itself a procedure.. This concept is an extremely powerful and versatile programming tool, because it allows programmers to modify certain steps of a library procedure in arbitrarily complicated ways, without having to understand or modify the code of that procedure.
User-defined functions should not be confused with stored procedures. Stored procedures allow the user to group a set of SQL commands. A procedure can accept parameters and execute its SQL statements depending on those parameters. A procedure is not an expression and, thus, cannot be used like user-defined functions.