Advanced Tools and Techniques

17Copyright © 2004, Oracle. All rights reserved.

Advanced Tools and Techniques

17-2 Copyright © 2004, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to:

• Generate scripts using SQL queries

• Use Dynamic SQL to automate script generation

• Create an external table

• Retrieve user context variables

• Issue statements that can be suspend upon encountering space condition errors


Using SQL to Generate Scripts

• Query dictionary tables

• Spool output to a file

• Use SQL*Plus or iSQL*Plus settings to remove unneeded text

• Use literals and concatenation characters to create SQL commands

SET HEAD OFFSET FEEDBACK OFFSPOOL drop_user_tables.sql

SELECT 'DROP TABLE ' || table_name || ';'FROM user_tables;


Example: Compiling Invalid Objects

SET HEAD OFFSET FEEDBACK OFFSPOOL compile_invalid_objects.sql

SELECT 'ALTER ' || object_type || ' ' || owner||'.'||object_name||' COMPILE;'FROM DBA_OBJECTSWHERE status = 'INVALID'AND object_type NOT IN ('PACKAGE BODY','TYPE BODY', 'SYNONYM');

SELECT 'ALTER PACKAGE ' || owner || '.' || object_name || ' COMPILE BODY;'FROM DBA_OBJECTSWHERE status != 'VALID'AND object_type = 'PACKAGE BODY';


What Is a Procedure?

• A procedure is a type of subprogram that performs an action.

• A procedure can be stored in the database, as a schema object, for repeated execution.

CREATE [OR REPLACE] PROCEDURE procedure_name [(parameter1 [mode1] datatype1, parameter2 [mode2] datatype2, ...)]IS | AS<PL/SQL Block>;


PL/SQL Procedures

Callingenvironment

Procedure

(DECLARE)

BEGIN

EXCEPTION

END;

IN parameter

OUT parameter

IN OUT parameter


Using IN and OUT Parameters

CREATE OR REPLACE PROCEDURE gen_rebuild_idx_script (schema IN VARCHAR2) ISBEGIN FOR idx IN (SELECT owner, index_name FROM ALL_INDEXES WHERE owner = schema) LOOP DBMS_OUTPUT.PUT_LINE('ALTER INDEX ' || idx.owner || '.' || idx.index_name || ' REBUILD;'); END LOOP;END gen_rebuild_idx_script;/

SET head OFFSET feedback OFFSPOOL rebuild_indexes.sql

EXEC gen_rebuild_idx_script('HR');


Using Native Dynamic SQL

Dynamic SQL:

• Is a SQL statement that contains variables that can change during runtime

• Is a SQL statement with placeholders and is stored as a character string

• Enables general-purpose code to be written

• Enables data-definition, data-control, or session-control statements to be written and executed from PL/SQL

• Is written using either DBMS_SQL or native dynamic SQL


The EXECUTE IMMEDIATE Statement

• INTO is used for single-row queries and specifies the variables or records into which column values are retrieved.

• USING is used to hold all bind arguments. The default parameter mode is IN.

EXECUTE IMMEDIATE dynamic_string [INTO {define_variable [, define_variable] ... | record}] [USING [IN|OUT|IN OUT] bind_argument [, [IN|OUT|IN OUT] bind_argument] ... ];


Dynamic SQL Using EXECUTE IMMEDIATE

CREATE PROCEDURE del_rows (p_table_name IN VARCHAR2, p_rows_deld OUT NUMBER)ISBEGIN EXECUTE IMMEDIATE 'DELETE FROM '||p_table_name; p_rows_deld := SQL%ROWCOUNT;END;/

VARIABLE deleted NUMBEREXECUTE del_rows('test_employees', :deleted)PRINT deleted


Dynamic SQL Example

DECLARE sql_stmt VARCHAR2(1024); CURSOR get_obj IS SELECT object_name, owner FROM ALL_OBJECTS WHERE owner = UPPER('&schema_name') AND object_type IN ('PACKAGE','FUNCTION','PROCEDURE','TYPE'); BEGIN FOR rec IN get_obj LOOP sql_stmt := 'CREATE PUBLIC SYNONYM '||rec.object_name||' FOR '||rec.owner||'.' ||rec.object_name; DBMS_OUTPUT.PUT_LINE(sql_stmt); EXECUTE IMMEDIATE sql_stmt; END LOOP;END;/


External Tables

The Oracle Database enables the transparent access, processing, and integration of external flat files:

• Transparent access of external data from within the database

• Highly efficient procedural processing of complex data structures

• Optimal integration into SQL for bulk processing


External Tables and the Oracle Database

Oracle Database

10, 50 ml Beaker, .., 22.00, 5.0020, 50 ml Conical Flask, ... ,25.50, 8.5030, 50 ml Measuring Cylinder, ...,50.00, 9.0040, ...

Data in the external file

PRODUCTS_EXT

PROD_ID PROD_NAME ... PRICE DISCOUNT

10 50 ml Beaker 22.00 5.0020 50 ml Conical Flask 25.50 8.5030 50 ml Measuring Cylinder 50.00 9 .00...

CREATE TABLE PRODUCTS_EXT…;

SELECT .. FROM PRODUCTS_EXT;


External Tables: Example

CREATE OR REPLACE DIRECTORY trace_files AS '/u01/app/oracle/admin/orcl/bdump';

CREATE TABLE alert_log ( line_text VARCHAR2(80) )ORGANIZATION EXTERNAL( TYPE ORACLE_LOADER DEFAULT DIRECTORY trace_files ACCESS PARAMETERS ( RECORDS DELIMITED BY NEWLINE BADFILE 'rejects.bad' LOGFILE 'output.log' FIELDS (line_text CHAR(80)) ) LOCATION ('alert_orcl.log'))REJECT LIMIT UNLIMITED;


Retrieving User Context Attributes

Retrieve the following information:

• The name of the user who logged onto the database

• The method by which that user was authenticated

SQL> SELECT SYS_CONTEXT ('USERENV', 2> 'SESSION_USER') "USER",3> SYS_CONTEXT ('USERENV', 4> 'AUTHENTICATION_TYPE') Auth_meth

5> FROM DUAL;

USER AUTH_METH----------------- --------------------OE DATABASE


Resumable Statements

A resumable statement:

• Allows you to suspend large operations instead of receiving an error

• Gives you a chance to fix the problem while the operation is suspended, rather than starting over

• Is suspended for these conditions:– Out of space– Maximum extents reached– Space quota exceeded


Using Resumable Space Allocation

• Queries, DML operations, and certain DDL operations can be resumed if they encounter an out-of-space error.

• A resumable statement can be issued through SQL, PL/SQL, SQL*Loader, or the Oracle Call Interface (OCI).

• To run a resumable statement, you must first enable resumable statements for your session.

ALTER SESSION ENABLE RESUMABLE;

INSERT INTO sales_new SELECT * FROM sh.sales;

ALTER SESSION DISABLE RESUMABLE;


Resuming Suspended Statements

SQL Statement EMPLOYEES table

Suspended

EMPLOYEES table

Free space

Used block

Continue SQL operation

AFTER SUSPEND

triggerABORT


Summary

In this lesson, you should have learned how to:

• Generate scripts using SQL queries

• Use Dynamic SQL to automate script generation

• Create an external table

• Retrieve user context variables

• Issue statements that can be suspend upon encountering space condition errors


Practice 17 Overview: Using Dynamic SQL

This practice covers the following topics:

• Using Dynamic SQL

• Retrieving user context information

Advanced Tools and Techniques

Documents