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A function is a subprogram that returns a value. The data type of the value is the data type of the function. A function invocation (or call) is an expression, whose data type is that of the function.
Before invoking a function, you must declare and define it. You can either declare it first (with function_declaration) and then define it later in the same block, subprogram, or package (with function_definition) or declare and define it at the same time (with function_definition).
Note:This topic applies to nested functions. For information about standalone functions, see "CREATE FUNCTION Statement". For information about package functions, see "CREATE PACKAGE Statement".
Declares a function, but does not define it. The definition must appear later in the same block, subprogram, or package as the declaration.
Tells the optimizer that the function returns the same value whenever it is invoked with the same parameter values (if this is not true, then specifying
DETERMINISTIC causes unpredictable results). If the function was invoked previously with the same parameter values, the optimizer can use the previous result instead of invoking the function again.
Do not specify
DETERMINISTIC for a function whose result depends on the state of session variables or schema objects, because results might vary across invocations. Instead, consider making the function result-cached (see "Making Result-Cached Functions Handle Session-Specific Settings" and "Making Result-Cached Functions Handle Session-Specific Application Contexts").
DETERMINISTIC functions can be invoked from a function-based index or a materialized view that has query-rewrite enabled. For more information and possible limitations of the
DETERMINISTIC option, see "CREATE FUNCTION Statement".
Use only with a table function, to specify that it is pipelined. A pipelined table function returns a row to its invoker immediately after processing that row and continues to process rows. To return a row (but not control) to the invoker, the function uses the "PIPE ROW Statement".
Note:You cannot run a pipelined table function over a database link. The reason is that the return type of a pipelined table function is a SQL user-defined type, which can be used only in a single database (as explained in Oracle Database Object-Relational Developer's Guide). Although the return type of a pipelined table function might appear to be a PL/SQL type, the database actually converts that PL/SQL type to a corresponding SQL user-defined type.
Enables the function for parallel execution, making it safe for use in slave sessions of parallel DML evaluations.
Caches the results of the function. For more information, see "PL/SQL Function Result Cache".
Name of the function that you are declaring or defining.
Specifies the data type of the value that the function returns, which can be any PL/SQL data type (see Chapter 3, "PL/SQL Data Types").
Restriction on datatype You cannot constrain this data type (with
NULL, for example). If
datatype is a constrained subtype, then the returned value does not inherit the constraints of the subtype (see "Formal Parameters of Constrained Subtypes").
Either defines a function that was declared earlier or both declares and defines a function.
Declares items that are local to the function, can be referenced in
body, and cease to exist when the function completes execution.
Required executable part and optional exception-handling part of the function. In the executable part, at least one execution path must lead to a
RETURN statement; otherwise, a runtime error occurs.
Specifies the data sources on which the results of the function depend. Each
data_source is the name of either a database table or view.
This clause is deprecated. As of Oracle Database 11g Release 2, the database detects all data sources that are queried while a result-cached function is running, and
relies_on_clause does nothing.
You cannot use
relies_on_clause in a function declared in an anonymous block.