The document provides an overview of Oracle architecture, including concepts such as schemas, tablespaces, and data dictionaries. It contrasts Oracle with other database systems like Access and MySQL, detailing its capabilities regarding files, roles, and permissions. Additionally, it touches on SQL functions, constraints, triggers, and best practices for indexes within Oracle databases.

1. ORACLE ARCHITECTURE
Overview
Presented By
Kelly Technologies
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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
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3. ORACLE
ARCHITECTURE
 database vs. instance
Parameter files*
Control files**
Data files
Redo Log files
System Global Area (SGA)
Background Processes
Disk Memory
Database Instance
* 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.
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4. ORACLE VS. ACCESS AND MYSQL
 Access
 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
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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
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6. MORE DATA DICTIONARY
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…
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7. ORACLE ODDS AND
ENDS
 Dual table
 % - the SQL wildcard
 inserting apostrophes
 Case sensitive string matching
INSERT INTO emp (name) VALUES (‘O’’Neill);
UPDATE emp
SET ename=UPPER(ename) WHERE ename='O''Neill';
SELECT 1+1*400 FROM DUAL;
SELECT ename FROM emp WHERE ename like ‘%neil%’;
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8. SYSDATE
 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
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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
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10. OUTER JOINS IN ORACLE
 Add (+) to table where nulls are acceptable
SELECT *
FROM emp, dept
WHERE emp.deptno(+)=dept.id;
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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()
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12. MORE FUNCTIONS
 nvl()
 If NULL, return this instead…
Nvl(lastname,’Anonymous’)
 decode()
 Sort of like an If/Then statement…
Decode(gender,0,’Male’,1,’Female’,’Unknown’)
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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
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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'))
);
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15. 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
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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;
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17. MORE OBJECTS
 Sequences
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
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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
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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
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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';
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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;
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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
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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)
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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
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25. THANK
YOU
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