Download Introduction to Databases

Using Procedures & Functions
Oracle Database PL/SQL 10g Programming
Chapter 9
Using Procedures & Functions
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Data Dictionary
Subprograms
Definer Rights
Invoker Rights
Purity Levels
Multiple-Valued Functions
Shared Pool
Oracle Database PL/SQL 10g Programming
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Using Procedures & Functions
Data Dictionary: Locations
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Stored Program Catalog Views:
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Definition views:
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Stored Program Source –
USER_SOURCE
Stored Program Information –
USER_PROCEDURES
Stored Program Header –
USER_ARGUMENTS
Stored Program Settings –
USER_PLSQL_OBJECT_SETTINGS
Dependency view:
USER_DEPENDENCIES
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Oracle Database PL/SQL 10g Programming
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Using Procedures & Functions
Data Dictionary: Locations
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Object Catalog Views:
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Object definitions:
USER_SOURCE
Table definitions:
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Table Structure –
USER_TABLES
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USER_TAB_COLS
Trigger definitions:
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Table Columns –
Trigger Structure –
USER_TRIGGERS
Trigger Columns –
USER_TRIGGER_COLS
Oracle Database PL/SQL 10g Programming
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Using Procedures & Functions
Data Dictionary: Query Status
SQL>
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SELECT
,
,
FROM
object_name
object_type
status
user_objects;
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Data Dictionary: Query Tables
SQL>
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SELECT
,
,
,
FROM
ORDER BY
,
table_name
column_id
column_name
data_type
user_tab_cols
table_name
column_id;
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Using Procedures & Functions
Data Dictionary: Query Programs
SQL>
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SELECT
,
FROM
WHERE
line
text
user_source
name = UPPER('program_name‘);
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Using Procedures & Functions
Package Specification Subprograms: Rules
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Stored Package Specification Programs:
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Are stored in compiled p-code, like Java byte
code.
Can be called by any other block.
Are modularized into smaller program units.
Compiled p-code can be pinned in the SGA for
faster execution.
Can be overloaded.
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Using Procedures & Functions
Package Subprograms: Stored
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Package stored subprograms:
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Are defined as procedures in the package specification.
Are defined as functions in the package specification.
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Can use schema defined types from the package specification.
Can use schema defined SQL types.
Can use locally defined types from package body ONLY in their
internal implementation:
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Locally defined types can declared in local subprogram as variables.
Locally defined types cannot be used as parameter data types.
Locally defined types cannot be used as function return data types.
Can be called from any schema PL/SQL program.
Stored functions CANNOT be called from SQL when they return a
PL/SQL data type.
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Using Procedures & Functions
Package Subprograms: Stored
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Package stored subprogram referencing:
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Do not require forward referencing:
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The specification publishes their definitions.
The body relies on the specification to avoid forward referencing
issues.
Package stored subprogram overloading:
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Signature rules:
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The list of formal parameters must differ by either:
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The position and type of formal parameters.
The number of formal parameters.
The function signature may change based on the return data type.
Oracle Database PL/SQL 10g Programming
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Using Procedures & Functions
Package Body (Local) Subprograms: Rules
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Local Package Body Programs:
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Are stored in compiled p-code, like Java byte
code.
Can be called ONLY by package blocks.
Tightly coupled design.
Compiled p-code cannot be pinned in the
SGA.
Can be overloaded only within the same
block.
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Using Procedures & Functions
Package Subprograms: Local
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Package local subprograms:
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Are defined as procedures in the package body.
Are defined as functions in the package body.
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Require forward referencing, like anonymous block subprograms.
Package local subprogram overloading:
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Can ONLY be called from a package body program unit.
Package local subprogram referencing:
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Can use locally defined types from the package body.
Can use schema defined types from package specifications.
Can use schema defined SQL types.
Follows the same rules as stored subprograms.
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Using Procedures & Functions
Package Subprograms: Dependencies
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Timestamp Model (default):
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Signature Model:
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Checks to make sure that dependents have an early
compilation timestamp.
Cannot resolve distributed timestamps in different
timezones.
Checks to make sure that the signature for functions
and procedures do not change between compilations.
Works in distributed configurations without impacts of
region timezones.
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Using Procedures & Functions
Package Subprograms: Serially Reusable
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Non-Serially Reusable (default):
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Serially Reusable:
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Runtime state is kept in process memory between
calls during a session.
Requires memory in the SGA for all logged-on users.
Runtime state is refreshed after each database call.
Requires memory in the SGA for users concurrently
calling the same program.
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Using Procedures & Functions
Definer Rights: Description
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Definer rights
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Is the default when creating stored programs.
Means that the stored program executes with the
same privileges as the defining user.
Can mean that calling the stored programs lets it run
against any schema level data.
Typically means that users only access a slice of data
in any schema, like a private virtual database.
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Using Procedures & Functions
Definer Rights: Depiction
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User #1
User #3
User #2
User #4
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Invoker Rights: Description
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Invoker rights
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Is the override when creating stored programs.
Means that the stored program executes with the
local privileges, which generally differ from the
definer’s privileges.
Typically means that users only access their own
schema data, like a distributed or local database.
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Invoker Rights: Depiction
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User #1
User #3
User #2
User #4
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Purity Level: Defined
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Purity levels restrict the behavior of stored programs.
Purity level guarantees are optional beginning with
Oracle 8i.
Purity levels are:
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Writes no database states (WNDS), which disallows DML
statements, like INSERT, UPDATE and DELETE.
Reads no database states (RNDS), which disallows DQL
statements, like SELECT.
Writes no package states (WNPS), which disallows changes to
package variables by assignment operations (including the
FETCH cursor INTO variable syntax).
Reads no package states (RNPS), which disallows assigning any
package variable values.
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Using Procedures & Functions
Multiple-Valued Functions: Defined
A multiple-valued function exists when the
return type of a stored or local function
returns a system reference cursor, or a
user-defined data type that has multiple
rows.
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Multiple-Valued Functions: Rules
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A multiple-valued functions must return the
value to the same type variable, which is done
by:
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Assignment in a calling PL/SQL block.
Assignment to a bind variable using a system
reference cursor.
A multiple-valued function returning a PL/SQL
variable can ONLY be used inside another
PL/SQL block.
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Using Procedures & Functions
Shared Pool: Pinning
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Pinning in the SGA shared pool can accelerate
and guarantee behavior of frequently called
stored programs:
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This places the p-code in the shared pool.
This prevents the least used algorithm from removing
it inbetween calls to it.
The DBMS_SHARED_POOL.KEEP enables
pinning a stored program into the SGA.
The DBMS_SHARED_POOL.UNKEEP removes a
pinned stored program from the SGA.
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Summary
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Data Dictionary
Subprograms
Definer Rights
Invoker Rights
Purity Levels
Multiple-Valued Functions
Shared Pool
Oracle Database PL/SQL 10g Programming
(Chapter 9)
Page 23