1. Oracle Architecture
Overview

2. Oracle terms Schema – logical collection of user’s objects
Tablespace – logical space used for storage
Datafile – physical file used for storage
Extent – group of contiguous blocks
Block – unit of physical storage

3. System Global Area (SGA)
Oracle Architecture
database vs. instance
Database
Instance
Parameter files*
Control files**
Data files
Redo Log files
System Global Area (SGA)
Background Processes
Memory
Disk
* Parameter files include the init<SID>.ora and config<SID>.ora files. These are used to set options for the database.
** Control files contain information about the db in binary form. They can be backed up to a text file however.

4. Oracle vs. Access and MySQL
One .mdb file contains all objects
Limited roles/permissions
MySQL
Three files per table
Permissions based on user, database, and host
Oracle
Many files
Many roles/permissions possible

5. The Oracle Data Dictionary
Collection of tables and views that show the inner workings and structure of the db
“static” data dictionary views
owned by SYS
created by catalog.sql script at db creation
contain DDL info
dynamic data dictionary views
also referred to as V$ views
based on virtual tables (X$ tables)
provide info about the instance

6. More Data Dictionary 1. Samples table created in user’s schema
Create table samples (
ID number(3) primary key,
Type varchar2(5),
Constraint type_ck check (type in (‘photo’,’swatch’))
…);
1. Samples table created in user’s schema
2. Primary key index created in user’s schema (SYS_C984620)
3. Data dictionary is also updated, with rows being inserted into tables underlying the following data dictionary views:
User_objects
User_constraints
User_cons_columns
And lots more…

7. Oracle Odds and Ends Dual table % - the SQL wildcard
inserting apostrophes
Case sensitive string matching
SELECT 1+1*400 FROM DUAL;
SELECT ename FROM emp WHERE ename like ‘%neil%’;
INSERT INTO emp (name) VALUES (‘O’’Neill);
UPDATE emp
SET ename=UPPER(ename) WHERE ename='O''Neill';

8. Sysdate ADATE Sysdate returns current system date AND time
use trunc function to remove time piece
Example:
select to_char (adate, ‘dd-mon-yy hh24:mi:ss’)
TO_CHAR(ADATE, ‘DD-MON-YY:HH24:MI:SS’)
17-feb-00 23:41:50
select adate from samples where trunc(adate)=‘17-feb-00’;
ADATE
17-FEB-00

9. ROWID
ROWID is an internal number Oracle uses to uniquely identify each row
NOT a primary key! Is the actual location of a row on a disk. Very efficient for retrieval.
Format specifies block, row, and file (and object in 8)
Oracle 7: BBBBBBB.RRRR.FFFFF
Oracle 8: OOOOOO.FFF.BBBBBB.RRR
Called pseudo-column since can be selected

10. Outer joins in Oracle Add (+) to table where nulls are acceptable
SELECT *
FROM emp, dept
WHERE emp.deptno(+)=dept.id;

11. Oracle SQL functions Upper(), lower()
Substr(), replace(), rtrim(), concat()
Length()
Floor(), sqrt(), min(), max(), stddev()
Add_months(), months_between(), last_day()
To_date(), to_char(), to_lob()

12. More functions nvl() decode() If NULL, return this instead…
Nvl(lastname,’Anonymous’)
decode()
Sort of like an If/Then statement…
Decode(gender,0,’Male’,1,’Female’,’Unknown’)

13. Oracle error messages
Divided into groups by first three letters (e.g. ORA or TNS)
Number gives more information about error
Several messages may be related to only one problem
oerr facility

14. Constraints Primary key Foreign key Unique, not null Check
Name your constraints
User_constraints, user_cons_columns
CREATE TABLE test (
id NUMBER(2),
col2 VARCHAR2(2),
col3 VARCHAR2(3),
CONSTRAINT test_pk PRIMARY KEY(id),
CONSTRAINT col3_ck CHECK (col3 IN ('yes','no')) );

15. NAME T SEARCH_CONDITION --------------- - -------------------------
SELECT
user_constraints.constraint_name name,
constraint_type type,
user_constraints.search_condition
FROM user_constraints, user_cons_columns
WHERE
user_constraints.table_name=user_cons_columns.table_name
AND user_constraints.constraint_name=user_cons_columns.constraint_name
AND user_constraints.owner=user_cons_columns.owner
AND user_constraints.table_name=‘TEST’;
NAME T SEARCH_CONDITION
COL3_CK C col3 IN ('yes','no')
TEST_PK P

16. Constraints Oracle naming of constraints is NOT intuitive!
enabling and disabling
disable constraint constraint_name;
the EXCEPTIONS table
run utlexcpt.sql to create EXCEPTIONS table then
alter SQL statement:
SQL_query EXCEPTIONS into EXCEPTIONS;
What constraints do *YOU* have in your schema?
@h:\..\chaffin\shared\scripts\utlexcpt.sql

17. More objects Sequences Synonyms creating the sequence
create sequence CustomerID increment by 1 start with 1000;
selecting from the sequence
insert into customer (name, contact, ID) values (‘TManage’,’Kristin Chaffin’,CustomerID.NextVal);
CurrVal is used after NextVal for related inserts
Synonyms
provide location and owner transparency
Can be public or private

18. PL/SQL - Triggers Executed on insert, update, delete
Use to enforce business logic that can’t be coded through referential integrity or constraints
Types of triggers
row level (use FOR EACH ROW clause)
statement level (default)
Before and After triggers
Referencing old and new values

19. Trigger example SQL> desc all_triggers; Name Null? Type
OWNER VARCHAR2(30)
TRIGGER_NAME VARCHAR2(30)
TRIGGER_TYPE VARCHAR2(16)
TRIGGERING_EVENT VARCHAR2(75)
TABLE_OWNER VARCHAR2(30)
BASE_OBJECT_TYPE VARCHAR2(16)
TABLE_NAME VARCHAR2(30)
COLUMN_NAME VARCHAR2(4000)
REFERENCING_NAMES VARCHAR2(128)
WHEN_CLAUSE VARCHAR2(4000)
STATUS VARCHAR2(8)
DESCRIPTION VARCHAR2(4000)
ACTION_TYPE VARCHAR2(11)
TRIGGER_BODY LONG

20. Trigger example (cont.)
SQL> select trigger_name from all_triggers where owner='SCOTT';
TRIGGER_NAME
AFTER_INS_UPD_ON_EMP
set lines 120
col trigger_name format a20
col triggering_event format a18
col table_name format a10
col description format a26
col trigger_body format a35
select trigger_name, trigger_type, triggering_event,
table_name, status, description, trigger_body
from all_triggers
where trigger_name='AFTER_INS_UPD_ON_EMP';

21. Trigger example (cont.)
SQL> /
TRIGGER_NAME TRIGGER_TYPE TRIGGERING_EVENT TABLE_NAME STATUS DESCRIPTION
TRIGGER_BODY
AFTER_INS_UPD_ON_EMP BEFORE EACH ROW INSERT OR UPDATE EMP ENABLED scott.after_ins_upd_on_emp
before insert or update
on scott.emp
for each row
begin
:new.ename := upper(:new.ename);
end;
The above trigger was created with the following statement:
create or replace trigger scott.after_ins_upd_on_emp
before insert or update on scott.emp
for each row
begin
:new.ename := upper(:new.ename);
end;

22. Remember those views? Query USER_TRIGGERS to get trigger info
Query USER_SOURCE to get source of procedure, function, package, or package body
Query USER_ERRORS to get error information (or use show errors)
col name format a15
col text format a40
select name, type, text
from user_errors
order by name, type, sequence;
Query USER_OBJECT to get status info

23. Understanding Indexes
Index overhead
impact on inserts, updates and deletes
batch inserts can be slowed by indexes - may want to drop, then recreate
rebuilding indexes
Use indexes when query will return less than 5% of rows in a large table
Determining what to index
All primary and foreign keys
Examine SQL and index heavily hit, selective columns (columns often found in where clauses)

24. What not to Index…preferably
columns that are constantly updated
columns that contain a lot of null values
columns that have a poor distribution of data
Examples:
yes/no
true/false
male/female

25. B*-tree index Branch blocks Leaf blocks Miller Deal – ROWID
< Davis
Davis
Jones
Smith
Turner
Turner >
Adams
Brown
Culver
Deal
Howard
Isis
Jules
Klein
Main
Moss
Porter
Sikes
Sykes
Thomas
Topper
Vera
Wagner
Yanks
1+ levels of branch blocks – these contain info about range of values contained in next level.
Only 1 level of leaf blocks – contain actual index values and rowids for associated rows
“Depth” of index refers to the number of branch levels between the root and leaf blocks.
Reverse key index reverses the values before storing them (e.g. value of ‘ABCD’ would be stored as ‘DCBA’) – this tends to address the problem of standard b*tree indexes where they become unbalanced over time (and thus less efficient and deeper, requiring more depth on the right side than the left side due to growth and deletion of values over time).
Function-based indexes can be either b*tree or bitmap and are simply based on the results of a function, rather than on the value of a row.
Leaf
blocks
Deal – ROWID
Howard – ROWID
Isis - ROWID
Detail of
leaf node
Figure in Oracle Essentials (2001). Greenwald, et.al. O’Reilly. p 92

26. Bitmap index Parts table Bitmapped index on ‘color’ partno color size1 2 3 4
GREEN
RED
RED BLUE
MED MED SMALL LARGE
Bitmapped index on ‘color’
color = ‘BLUE’
color = ‘RED’
color = ‘GREEN’
Part number
Figure in Oracle Essentials (2001). Greenwald, et.al. O’Reilly. p 95