Trigger Writing For Fun and Profit

8/9/2019 Trigger Writing For Fun and Profit

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A Community of Learning

SUNGARD SUMMIT 2007 | sungardsummit.com 1

Trigger Writing

for Fun and Profit

Presented by: Larry Holder

Database Administrator

The University of Tennessee at Martin

March 21, 2007

Course ID: 2


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Session Rules of Etiquette

Please set your cell phone or pager on stun.

If you must leave the session early, please do so as

discreetly as possible, and dont let the door hit you on

the way out.

Please avoid side conversation during the session,

unless you are discussing what a fantastic job Im doing

up here...

Thanks a Gigabyte!


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Introduction

This session provides an introduction to writing

database triggers, along with several real-world

examples that can enhance your support and

functionality of Banner.


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A Community of Learning

SUNGARD SUMMIT 2007 | sungardsummit.com 4

Whats a Trigger?


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Whats a Trigger?

We aint talkin

about Roys

noble steed...


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Ok, so... whats a trigger?

A PL/SQL object, akin to a Procedure.

Most often, a cool, calm & calculated reaction to an

event, such as insert, update, delete, or even select, ona table.

Sometimes, a reaction to a database event, such as a

user logging onto the database.


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What can I do with it?

Modify a field before it is inserted or updated.

Insert, update, or delete data in other tables.

Perform additional error-checking, and prevent an

unwanted insert, update, or delete from occurring.

Notify someone by email about an event.


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What schema owns the custom triggers?

We chose to let SATURN own our custom triggers

associated with SATURN-owned tables; likewise for

GENERAL, WTAILOR, etc.

Be sure the owner of the trigger is granted rights on anytables it references or modifies that are owned by

another schema.


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What naming convention is used?

UTM_ST_SARADAP_PRE_IU_ROW

A pre-insert / update trigger, at the row level, on the

table SARADAP. UTM is our prefix, and ST is

standard for Student Trigger.

Remember30-character object name max within

Oracle.

Add numeric suffix if a tie-breaker is needed (multiple

triggers on same table are allowed).


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Special variables

:old.spraddr_street_line1

meaningless for INSERT, will yield NULL

:new.spraddr_street_line1


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Special variables

INSERTING, UPDATING, DELETING

Useful if trigger handles more than one mode, such

as both INSERT and UPDATE, and your logic needs

to know which occurred.

IF INSERTING THENdo this;

ELSEdo that;

END IF;


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Special variables

USER - the Oracle userid of who is connected

For self-service, keep in mind that the userid is likely

something like WWW_USER.

SYSDATE - the current date and time

DATABASE_NAME

Useful to differentiate between production and test:

IF substr(DATABASE_NAME,1,4) = 'PROD'


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Examples of Before/After & Row/Statement

create or replace trigger trigger_name

BEFORE INSERT or UPDATE on table_name for each ROW

create or replace trigger trigger_name

AFTERDELETE on table_name

statement level if no

"for each row"Firing order:

1. Before Statement (once only)

2. Before Row (once per each affected row)3. The actual DML statement

4. After Row (once per each affected row)

5. AfterStatement (once only)


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Example: Modifying fields "before"

create or replace trigger utm_st_sarpers_pre_in_up_row

BEFORE INSERT or UPDATE on SARPERS for each ROW

BEGIN

IF :new.sarpers_last_name IS NOT NULL THEN

IF :new.sarpers_last_name = UPPER(:new.sarpers_last_name) OR

:new.sarpers_last_name = LOWER(:new.sarpers_last_name) THEN

:new.sarpers_prefix := INITCAP(:new.sarpers_prefix);

:new.sarpers_first_name := INITCAP(:new.sarpers_first_name);

:new.sarpers_middle_name1 := INITCAP(:new.sarpers_middle_name1);

:new.sarpers_middle_name2 := INITCAP(:new.sarpers_middle_name2);

:new.sarpers_last_name := INITCAP(:new.sarpers_last_name);

:new.sarpers_suffix := INITCAP(:new.sarpers_suffix);

:new.sarpers_nickname := INITCAP(:new.sarpers_nickname);

:new.sarpers_combined_name := INITCAP(:new.sarpers_combined_name);

:new.sarpers_former_name := INITCAP(:new.sarpers_former_name);

END IF;

END IF;

END;

/


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Example: Writing to an additional table

create or replace trigger utm_st_sarctrl_post_ins_row

AFTER INSERT on SARCTRL for each ROW

DECLARE

PRAGMA AUTONOMOUS_TRANSACTION;

BEGIN

insert into saraatt

values (:new.sarctrl_pidm,

:new.sarctrl_term_code_entry,

:new.sarctrl_appl_no_saradap,

'WAPP',

sysdate);

COMMIT;

EXCEPTION

WHEN OTHERS THEN

NULL;

COMMIT;

END;

/

Note the use, in this

example, of

autonomoustransaction, if you wish

or need to commit an

action independently of

the transaction causing

the trigger. Otherwise, a

trigger cannot include acommit.


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Example: Additional error checking

c

reate or replac

e trigger utm_st_spriden_pre_insert_rowBEFORE INSERT on SPRIDEN for each ROWBEGIN

IF :new.spriden_change_ind IS NULL THENIF (SUBSTR(:new.spriden_id,1,3) = '960' OR

SUBSTR(:new.spriden_id,1,1) = '-')OR(SUBSTR(:new.spriden_id,1,1) > '9' AND :new.spriden_entity_ind = 'C')

OR(LENGTH(:new.spriden_id)


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Example: Sending an email notification

create or replace trigger utm_st_sortest_post_del_row

after DELETE on SORTEST for each ROW

w_conn UTL_SMTP.connection;w_crlf varchar2(2) := CHR(13) || CHR(10); w_mailhost varchar2(30) := 'your_email_server'; w_mesg varchar2(4000); w_from varchar2(30) := 'your_from_address'; w_to varchar2(30) := 'your_recipient_address';

w_test_email varchar2(30) := 'your_reciepient_for_non_production'; w_stu_id varchar2(9); w_stu_name varchar2(100);

BEGINBEGIN

IF SUBSTR(DATABASE_NAME,1,4) != 'PROD' THENw_to := w_test_email;

END IF;

select spriden_id, spriden_first_name || ' ' || spriden_last_nameinto w_stu_id, w_stu_namefrom spriden

where spriden_pidm = :old.sortest_pidmand spriden_change_ind is null; continued . . .


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Example: Sending an email... (continued)

w_mesg :='Date: ' || TO_CHAR(SYSDATE,'DD Mon YY HH24:MI:SS') || w_crlf ||'From: ' || w_from || w_crlf ||'Subject: ' || 'Deletion from SORTEST (SOATEST)' || w_crlf ||'To: ' || w_to || w_crlf || w_crlf ||user || ' deleted an entry for ' || w_stu_name || ' (' || w_stu_id || ') of' ||': code = ' || :old.sortest_tesc_code ||', date = ' || to_char(:old.sortest_test_date,'MM-DD-YYYY') ||', score = ' || :old.sortest_test_score ||

w_c

rlf || w_c

rlf || ' ' || w_c

rlf;

w_conn := UTL_SMTP.open_connection(w_mailhost, 25);UTL_SMTP.helo(w_conn, w_mailhost);UTL_SMTP.mail(w_conn, w_from);UTL_SMTP.rcpt(w_conn, w_to);UTL_SMTP.data(w_conn, w_mesg);UTL_SMTP.quit(w_conn);

EXCEPTIONWHEN OTHERS THEN NULL;

END;END;/


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Disabling and enabling a trigger

alter trigger [owner.]name DISABLE;

alter trigger [owner.]name ENABLE;

Automatically enabled when initially created.

select * from dba_triggerswhere trigger_name like 'UTM%';


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Mutating trigger example

BEGIN

w_pidm := :new.spbpers_pidm; w_new_ssn := :new.spbpers_ssn;

IF :new.spbpers_ssn IS NOT NULL THENOPEN check_for_dup;FETCH check_for_dup INTO w_flag;CLOSE check_for_dup;

IF w_flag = 'Y' THENRAISE_APPLICATION_ERROR(-20501,'*** SSN already in use ***');

END IF;END IF;

END utm_junk1;/

create or replace trigger utm_junk1

BEFORE insert or update

of spbpers_ssn on SPBPERS

for each ROW

DECLARE

w_pidm spbpers.spbpers_pidm%type;

w_new_ssn spbpers.spbpers_ssn%type;w_flag char(1) := NULL;

CURSORcheck_for_dup IS

select distinct 'Y'

fromspbpers

where spbpers_ssn = w_new_ssn

and spbpers_pidm != w_pidm;


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Results (mutation) ...

ORA-04091: table SATURN.SPBPERS is mutating,trigger/function may not see it

ORA-06512: at "SATURN.UTM_JUNK1", line xx

ORA-06512: at "SATURN.UTM_JUNK1", line xxORA-04088: error during execution of trigger

'SATURN.UTM_JUNK1'


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Solution, part 1 of3 (package)

create or replace package utm_st_spbpers_pkg as

TYPE t_pidms IS TABLE OF spbpers.spbpers_pidm%TYPE INDEX BY BINARY_INTEGER;

TYPE t_new_ssns IS TABLE OF spbpers.spbpers_ssn%TYPE INDEX BY BINARY_INTEGER;

pidms t_pidms;

new_ssns t_new_ssns;

num_entries BINARY_INTEGER := 0;

END utm_st_spbpers_pkg;

/


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Solution, part 2 of3 (before / row)

create or replace trigger utm_st_spbpers_pre_iu_row

BEFORE insert or update of spbpers_ssn on SPBPERS

for each ROW

BEGIN

utm_st_spbpers_pkg.num_entries := utm_st_spbpers_pkg.num_entries + 1;

utm_st_spbpers_pkg.pidms (utm_st_spbpers_pkg.num_entries) :=

:new.spbpers_pidm;

utm_st_spbpers_pkg.new_ssns (utm_st_spbpers_pkg.num_entries) :=

:new.spbpers_ssn;

END utm_st_spbpers_pre_iu_row;


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Solution, part 3 of3 (after / statement)

create or replace trigger utm_st_spbpers_post_iu_stmt

AFTER insert or update of spbpers_ssn on SPBPERS

DECLARE

w_num_entries utm_st_spbpers_pkg.num_entries%type;

w_pidm spbpers.spbpers_pidm%type; w_new_ssn spbpers.spbpers_ssn%type;

w_flag char(1) := NULL;

w_error char(1) := 'N';

CURSORcheck_for_dup IS

select distinct 'Y'

from spbpers

where spbpers_ssn = w_new_ssn

and spbpers_pidm != w_pidm;

continued...


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BEGIN

w_num_entries := utm_st_spbpers_pkg.num_entries;

FOR z_index IN 1..w_num_entries LOOP

w_pidm := utm_st_spbpers_pkg.pidms (z_index);

w_new_ssn := utm_st_spbpers_pkg.new_ssns (z_index);

IF w_new_ssn IS NOT NULL THENOPEN check_for_dup;

FETCH check_for_dup INTO w_flag;

CLOSE check_for_dup;

IF w_flag = 'Y' THEN

w_error := 'Y';

END IF;

END IF;

END LOOP;

continued...


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IF w_error = 'Y' THEN

utm_st_spbpers_pkg.num_entries := 0;

RAISE_APPLICATION_ERROR(-20501, '*** SSN ALREADY IN USE ***');END IF;

utm_st_spbpers_pkg.num_entries := 0;

END utm_st_spbpers_post_iu_stmt;

/


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New Results (no mutation) ...

ORA-20501: *** SSN ALREADY IN USE ***

ORA-06512: at "SATURN.UTM_SPBPERS_POST_IU_STMT", line xx

ORA-04088: error during execution of trigger

'SATURN.UTM_SPBPERS_POST_IU_STMT'

This is expected

This is the application error

that we intentionally raised


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Banner7 "BTW..."

I've found that the new API logic of Banner7 has changed a few things...

for example, the column SGBSTDN_LEVL_CODE is still NULL wheninitially inserted; a subsequent Update populates it. I changed

several POST-INSERT triggers to POST-INSERT/UPDATE and added

the following logic at the beginning, to handle the initialsetting of the

column regardless of whether done by Insert or Update...

IF (INSERTING AND :new.sgbstdn_levl_code IS NULL) OR

(UPDATING AND :old.sgbstdn_levl_code IS NOT NULL) THEN

GOTO skip_everything;

END IF;

...

NULL;


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Helpful Debugging Tip

Consider creating a table to hold debug info, which you can write to

from any trigger that you are testing... to show you values in :oldand :new, for example, plus anything else you care to review. I used

this to debug the Post-Insert triggers mentioned on the previous

slide...

Create Table Trigger_Debug

(trigger_name varchar2(30) not null,

datetime date not null,codepoint varchar2(30) not null,

info1 varchar2(100),

info2 varchar2(100),

info3 varchar2(100);

Create Public Synonym Trigger_Debug for Trigger_Debug;

Grant All on Trigger_Debug to Public;

w_debug char(1) := 'Y'; turn this on oroff as needed

IF w_debug = 'Y' THEN

INSERT INTO TRIGGER_DEBUG VALUES

('MY_TRIGGER',SYSDATE,'BEGIN',

:OLD.SGBSTDN_LEVL_CODE, :NEW.SGBSTDN_LEVL_CODE, NULL);


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Summary

Triggers are a great way to extend the functionality of

Banner without introducing baseline modifications.

Rome wasnt built in a day. Start out simply, and add

more at your own pace.


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Questions & Answers

Ok, its your turn...


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Thank You!

Larry Holder

[email protected]

www.utm.edu/staff/lholder/dba

Please complete the online

class evaluation form

Course ID: 2

SunGard, the SunGard logo, Banner, Campus Pipeline, Luminis, PowerCAMPUS, Matrix, and Plus are

trademarks or registered trademarks ofSunGard Data Systems Inc. or its subsidiaries in the U.S. and other

countries. Third-party names and marks referenced herein are trademarks or registered trademarks of their

respective owners.

General presentation Copyright 2006 Larry Holder (of The University of Tennessee at Martin).

Portions 2006SunGard. All rights reserved.

Photo of Roy Rogers and Trigger used by permission of the Roy Rogers-Dale Evans Museum, Branson, MO.

No animals were harmed in the production of this presentation. No artificial ingredients added.

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Trigger Writing For Fun and Profit