co•he•sion noun \kō-ˈhē-zhən\ 1 : the act or state of sticking together tightly; especially: unity
Trigger Writing is
Alive and Well
Larry Holder
The University of Tennessee at Martin
Tuesday November 5, 1:30-2:30 pm
Course ID: 193
Welcome!
Come join me on an adventure in learning
the basics of writing database triggers,
including a look at several real-world
examples that can enhance your support
and functionality of Banner.
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What’s a Trigger?
We ain’t talkin’ about Roy’s
noble steed...
Ok, so... what’s a trigger?
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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, on a 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?
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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?
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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 any tables 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
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A pre-insert / update trigger, at the row level, on
the table SARADAP. “UTM” is our prefix, and “ST”
is standard for “Student Trigger”.
Remember 30-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
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meaningless for INSERT, will yield NULL
:new.spraddr_street_line1
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Special variables (2)
INSERTING, UPDATING, DELETING
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Useful if trigger handles more than one mode,
such as both INSERT and UPDATE, and your logic
needs to know which occurred.
IF INSERTING THEN
do this;
ELSE
do that;
END IF;
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Special variables (3)
USER - the Oracle userid of who is connected
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For self-service, keep in mind that the userid is
likely something like WWW_USER.
SYSDATE - the current date and time
DATABASE_NAME
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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
AFTER DELETE on table_name
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. After Statement (once only)
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statement level if no
"for each row"
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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;
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Note the use, in this
example, of
autonomous
transaction, if you wish
or need to commit an
action independently of
the transaction causing
the trigger. Otherwise, a
trigger cannot include a
commit.
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Example: Additional error checking
create or replace trigger utm_st_spriden_pre_insert_row
BEFORE INSERT on SPRIDEN for each ROW
BEGIN
IF :new.spriden_change_ind IS NULL THEN
IF (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) <= 7 AND :new.spriden_entity_ind =
'C')
THEN
NULL;
ELSE
RAISE_APPLICATION_ERROR
(-20501, 'UTM ERROR *** ADDING THIS ID VALUE IS BLOCKED');
END IF;
END IF;
END;
/
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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
w_crlf
w_mailhost
w_mesg
w_from
w_to
w_test_email
w_stu_id
w_stu_name
UTL_SMTP.connection;
varchar2(2) := CHR(13) || CHR(10);
varchar2(30) := 'your_email_server';
varchar2(4000);
varchar2(30) := 'your_from_address';
varchar2(30) := 'your_recipient_address';
varchar2(30) := 'your_reciepient_for_non_production';
varchar2(9);
varchar2(100);
BEGIN
BEGIN
IF SUBSTR(DATABASE_NAME,1,4) != 'PROD' THEN
w_to := w_test_email;
END IF;
select
into
from
where
and
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spriden_id, spriden_first_name || ' ' || spriden_last_name
w_stu_id, w_stu_name
spriden
spriden_pidm = :old.sortest_pidm
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_crlf || w_crlf || ' ' || w_crlf;
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);
EXCEPTION
WHEN OTHERS THEN NULL;
END;
END;
/
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Disabling and enabling a trigger
alter trigger [owner.]name DISABLE;
alter trigger [owner.]name ENABLE;
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Automatically enabled when initially created.
select * from dba_triggers
where trigger_name like 'UTM%';
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Mutating trigger example
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;
CURSOR
select
from
where
and
check_for_dup IS
distinct 'Y'
spbpers
spbpers_ssn
= w_new_ssn
spbpers_pidm != w_pidm;
BEGIN
w_pidm
w_new_ssn
:= :new.spbpers_pidm;
:= :new.spbpers_ssn;
IF :new.spbpers_ssn IS NOT NULL THEN
OPEN check_for_dup;
FETCH check_for_dup INTO w_flag;
CLOSE check_for_dup;
IF w_flag = 'Y' THEN
RAISE_APPLICATION_ERROR(-20501,
'*** SSN already in use ***');
END IF;
END IF;
END utm_junk1;
/
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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 xx
ORA-04088: error during execution of trigger
'SATURN.UTM_JUNK1'
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Solution, part 1 of 3 (package)
create or replace package utm_st_spbpers_pkg as
TYPE t_pidms
IS TABLE
spbpers.spbpers_pidm%TYPE
TYPE t_new_ssns IS TABLE
spbpers.spbpers_ssn%TYPE
OF
INDEX BY BINARY_INTEGER;
OF
INDEX BY BINARY_INTEGER;
pidms
new_ssns
t_pidms;
t_new_ssns;
num_entries
BINARY_INTEGER := 0;
END utm_st_spbpers_pkg;
/
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Solution, part 2 of 3 (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 of 3 (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
w_pidm
w_new_ssn
w_flag
w_error
CURSOR
select
from
where
and
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utm_st_spbpers_pkg.num_entries%type;
spbpers.spbpers_pidm%type;
spbpers.spbpers_ssn%type;
char(1) := NULL;
char(1) := 'N';
check_for_dup IS
distinct 'Y'
spbpers
spbpers_ssn
= w_new_ssn
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
w_new_ssn
:= utm_st_spbpers_pkg.pidms
(z_index);
:= utm_st_spbpers_pkg.new_ssns (z_index);
IF w_new_ssn IS NOT NULL THEN
OPEN check_for_dup;
FETCH check_for_dup INTO w_flag;
CLOSE check_for_dup;
IF w_flag = 'Y' THEN
w_error := 'Y';
END IF;
continued...
END IF;
END LOOP;
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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 ***
This is the application error
that we intentionally raised
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
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Another way – since 11g
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“Compound” Trigger introduced in 11g
Combines the 3 parts (package, before
row, and after statement)
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See Oracle 11g trigger documentation
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Thanks to Rob Pierce
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Compound Trigger
CREATE OR REPLACE TRIGGER MYTRIGGER
FOR UPDATE OF MYTABLE
COMPOUND TRIGGER
…
(declarations)
…
BEFORE STATEMENT IS
…
END BEFORE STATEMENT;
AFTER EACH ROW IS
…
END AFTER EACH ROW;
END MYTRIGGER;
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By the way…
The API logic introduced in Banner 7 changed a few things... for
example, the column SGBSTDN_LEVL_CODE is still NULL when initially
inserted; a subsequent Update populates it. I changed several POSTINSERT triggers to POST-INSERT/UPDATE and added the following
logic at the beginning, to handle the initial setting 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;
...
<<skip_everything>>
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 :old and
: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 or off
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 wasn’t built in a day. Start out simply,
and add more at your own pace.
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Questions & Answers
Ok, it’s your turn...
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Thank You!
Larry Holder
lholder@utm.edu
www.utm.edu/staff/lholder
Please complete the session evaluation form
Course ID 193
General presentation Copyright © 2006-2013 Larry Holder (of The University of Tennessee at Martin).
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. Mileage
may vary. All disclaimers apply.
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