ORACLE ARCHITECTURE Overview

Presented ByKelly Technologies

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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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ORACLE ARCHITECTURE

database vs. instance

Parameter files*Control files**

Data filesRedo 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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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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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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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 schema2. 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_objectsUser_constraintsUser_cons_columnsAnd lots more…

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ORACLE ODDS AND ENDS

Dual table

% - the SQL wildcard

inserting apostrophes

Case sensitive string matchingINSERT 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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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’;

ADATE17-FEB-00

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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.FFFFFOracle 8: OOOOOO.FFF.BBBBBB.RRR

Called pseudo-column since can be selected

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OUTER JOINS IN ORACLE

Add (+) to table where nulls are acceptable

SELECT *FROM emp, deptWHERE emp.deptno(+)=dept.id;

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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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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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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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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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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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CONSTRAINTS

Oracle naming of constraints is NOT intuitive!

enabling and disablingdisable 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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MORE OBJECTS Sequences

creating the sequencecreate sequence CustomerID increment by 1 start with 1000;

selecting from the sequenceinsert into customer (name, contact, ID) values (‘TManage’,’Kristin Chaffin’,CustomerID.NextVal);

CurrVal is used after NextVal for related inserts Synonyms

provide location and owner transparencyCan be public or private

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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 triggersrow level (use FOR EACH ROW clause)statement level (default)Before and After triggers

Referencing old and new values

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TRIGGER EXAMPLESQL> 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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TRIGGER EXAMPLE (CONT.)

SQL> select trigger_name from all_triggers where owner='SCOTT';

TRIGGER_NAME------------------------------AFTER_INS_UPD_ON_EMP

set lines 120col trigger_name format a20col triggering_event format a18col table_name format a10col description format a26col trigger_body format a35select trigger_name, trigger_type, triggering_event, table_name, status, description, trigger_bodyfrom all_triggerswhere trigger_name='AFTER_INS_UPD_ON_EMP';

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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 rowbegin :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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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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UNDERSTANDING INDEXES

Index overhead impact on inserts, updates and deletesbatch inserts can be slowed by indexes - may

want to drop, then recreaterebuilding indexes

Use indexes when query will return less than 5% of rows in a large table

Determining what to indexAll primary and foreign keysExamine SQL and index heavily hit, selective

columns (columns often found in where clauses)

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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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THANK YOU

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