Triggers & built-in packages

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1. trigger （ The principle of trigger should be explained clearly ）
2. Built in packages

One 、 trigger
    1. Three operations ：  delete   update   insert      
    2. Two temporary tables ：  :new   :old    
    3. Two time points ：   after    before
    4. Two important models ：   Row level     Sentence level
    5. Conditions ： when

    Oracle Trigger ratio in SQL Server To be complex ;
    SQL Server Only one event will be triggered by adding, deleting and modifying in , But in Oracle Two events will be triggered in .
    With delete For example ,Oracle There is a pre deletion event before 、 Event after deletion after.
    Oracle Trigger points ： Pre trigger 、 Post trigger

1. What is trigger ？
    (1) Trigger is a special stored procedure ;
    (2) Triggers cannot be called directly , It's not a manual start , It's triggered by events ;-- Additions and deletions
    (3) Triggers are often used to enforce data integrity constraints and business rules .
    (4) Trigger has the function of transaction .
    To put it simply ： A trigger is a switch , Be responsible for the light on and off , It lights up when you move it .

    Oracle Trigger ratio SQL Server It's more complicated , Before triggering before And after triggering after.

2. Create trigger Syntax （ The hardest thing in history oracle grammar , Not one of them. ）
create [or replace] trigger trigger_name
after|before|instead of                    --instead reverse
[insert][[or] update [of Column list ]][[or] delete]
on table Table or view                            -- View usage  
[referencing{:old [as] old/:new [as] new}]  -- Quote the new table and the old table
[for each row]                              -- Row level mode
[when(condition)]                           -- Conditions
pl/sql_block;                               --pl/sql sentence (begin...end)

insert  after  before

-- Case study ：
insert into emp values(…, Zhang San ,…,0,……);

==> Go to  :new

create or replace trigger trig_name
after insert
on emp
for each row
begin
    if(:new.sal=0) then
    dbms_output.put_line(' Warning ： You can't work without pay ');
    else
    dbms_output.put_line(' Record inserted ');
    end if;
end;

3. The trigger consists of three parts ：
   a. Trigger statements （ event ）-- Define the... That activates the trigger DML Events and DDL event ;
   b. Trigger limit       --- Conditions for executing triggers , This condition is true to activate the trigger ;
   c. Trigger action （ The main body ）-- contain SQL Statements and code , They run only when the trigger statement is issued and the value of the trigger limit is true .

    Notes ： The sequence is saved to the database through the pre trigger .

4. Schematic diagram of front trigger and back touch

5. Create trigger cases in cascading tables

-- Liswen cannot be deleted
  ( When to trigger ？a.delete when ; b.when When conditions are met ; c. The code states )

create or replace trigger t_studel
after delete
on stuinfo
for each row
begin
    if :old.stuname=' Lisbon ' then
    -- Throw an exception
    raise_application_error(-20010,' The student cannot delete ！！！');
    end if;
end;

delete from emp;

-- Liswen cannot be deleted , Can't change
after delete or update

-- How to know is (insert\delete\update) Which operation ？
……
begin
case
    when deleting then
    -- deleted
    if :old.stuname=' Lisbon ' then
        raise_application_error(-20010,' The student cannot delete ！！！');
        end if;

    when updating then
    -- When modifying
    if :old.stuname=' Lisbon ' then
        raise_application_error(-20011,' This student cannot modify ！！！');
        end if;

    when inserting then
    -- Insertion time
    if :old.stuname=' Zhang Yang ' then
        raise_application_error(-20012,' How dare you recruit this student ！！！');
        end if;

end case;
end;

insert Li Chao    :new

insert  before  ---->  if (:old   Li Chao    --->   Insert into the table == useless
                       if (:new   Li Chao    --->   Not inserted into the table

before--->:new

insert  after   ---->  if (:old   Li Chao )   --->   Insert into the table
                   if (:new   Li Chao )   --->   Not inserted into the table

before | after  insert  ----> :new
before | after  delete  ----> :old

====================================
reflection ：
A table can create several insert\update\delete trigger ？
====================================
Trigger of advanced point

-- And mirror pairs

1. Determine on which table the trigger is written  on table
2. Determine which trigger to use insert  delete   update
3. use after still before, use :new  :old

-- stay stuinfo Write a in the table delete trigger , Specify the name of the person to delete ,
Delete directly stumarks The score of the person in the table .

create or replace tirgger t_mydel
after delete
on stuinfo
for each row
    declare
    stu varchar2(22);
begin
    stu:=:old.stuno; -- Assign the student ID of the deleted student to the variable
    delete from stumarks where stuno=stu;
end;

-- Under operation
delete from stuinfo where stuname=' Lisbon ';

============================================
Be careful ：
Triggers for table joins are complex , Yes A Table operation triggers A Trigger for table , At the same time, the shadow arrived B Table triggers B Trigger for table , And so on ...

Suggest ： When tables are frequently associated with tables , It is recommended to use triggers .
============================================

Row level triggers and statement level triggers ：

-- Case study 2
create or replace tirgger t_mydel
after delete
on stuinfo
for each row
begin
    dbms_output.put_line(' Well deleted ！');
end;

-- perform （ Deleted a record , The result shows a ' Well deleted '）
delete from stuinfo where stuname=' Li Wencai ';

-- perform （ Deleted records in the entire table , Show N strip ' Well deleted '）
delete from stuinfo

-- explain ： This is how to explain row level triggers .
-- Line level triggers ： Delete one by one , Deleting an entry triggers a row level trigger .

    *********************************
     reflection ：
     If you will [for each row] Code deletion , Execute to see the effect .-- Statement level triggers .
    *********************************

-- Statement level triggers ： Execute a trigger once .

===========================================

Identity column ： Sequence + trigger
    
-- Create a new table , Ready to insert records , Use triggers and sequences .

create table tb_715(
    sid number,
    sname varchar2(22)
)

-- Perform the insert operation
insert into tb_715(sid,sname) values(1,' Liu Shuai ')

-- demand ： Don't write sid,1 Can help me automatically generate a sequence .

-- solve ：(1) Create sequence
create sequence seq715;
    (2) Create a trigger , Trigger before use , use new surface
create or replace trigger t_insert
before insert
on tb_715
for each row
begin
    -- In the new table id= The next value of the sequence
    select seq715.nextval into :new.sid from dual;
end;

*****************************************

oracle 11g The grammar of ：
    :new.sid:=seq715.nextval;

oracle 10g The grammar of ：
    select seq715.nextval into :new.sid from dual;

Don't use variables , The method of using variables is 11g Writing .

*****************************************

--:new surface , Put the inserted data into :new In the table , Confirm and put it in the table to be updated .

--:old surface , Put unwanted data into :old In the table , Confirm not to clear :old surface .

-- Be careful ：:new Table and :old There is only one piece of data in the table from beginning to end , How many columns are there ？ How many columns does the trigger's table have ,:new Table and :old How many columns does the table have .

commit;-- Submit

--oracle-06  trigger 
1. Trigger keywords ：trigger  
2. Trigger Overview ： Is a special stored procedure , The stored procedure is a special function 
3. effect ： When executed DML（insert,update,delete） When the sentence is , The trigger will be triggered automatically , Cannot call manually 
4. Usage scenario of trigger ：
#（1） You can limit the insertion of data 
#（2） You can limit the modification of data 
#（3） You can restrict the deletion of data 
#（4） a key ：a. cascading deletion  b. Sequence + trigger ===》 Simulate self growth 
5. The syntax of triggers （2322）
#  2: 2 Trigger time points ：after|before
#  3: 3 A trigger event  insert update delete
#  2: 2 A trigger mode    Statement level trigger mode       Row level trigger mode （for each row）
#  2: 2 Pseudo table      :new   :old
create or replace trigger  Trigger Name 
before|after
insert| update|delete
on tableName
for each row
	begin
		-- Executable modules ： Limit data 
		end;
--------------------------------------------------------------------

-- Create a student information table 
create table stuInfo
(
  stuNo varchar2(8) not null primary key,
  stuName varchar2(10) not null,
  stuSex varchar2(2) not null,
  stuAge number(6) not null,
  stuSeat number(6) not null,
  strAddress varchar2(255) default(' The address is unknown ')
)

go

-- Create a student information table 
create table stuInfo
(
  stuNo varchar2(8) not null primary key,
  stuName varchar2(10) not null,
  stuSex varchar2(2) not null,
  stuAge number(6) not null,
  stuSeat number(6) not null,
  strAddress varchar2(255) default(' The address is unknown ')
)

go

-- Create a student transcript 
create table stuMarks
(
  ExamNo varchar2(7) not null primary key,
  stuNo varchar2(6) not null references stuInfo(stuNo),
  writtenExam number(6) null,
  LabExam number(6) null
)

go

-- Insert test data into the student information table 
insert into stuInfo(stuNo, stuName, stuSex, stuAge,stuSeat,strAddress)
select 's25301', ' Zhang Qiuli ', ' male ', 18,1, ' Beijing haidian ' from dual union
select 's25303', ' Lisbon ', ' Woman ', 22,2, ' Heyang Luoyang ' from dual union
select 's25302', ' Li Wencai ', ' male ', 85, 3,' The address is unknown ' from dual union
select 's25304', ' Ouyang Junxiong ', ' male ', 28, 4,' xinjiang ' from dual union
select 's25318', ' Mei Chaofeng ', ' Woman ', 23, 5,' The address is unknown ' from dual

go

-- Insert test data into the student transcript 
insert into stuMarks(ExamNo, stuNo, writtenExam, LabExam)
select 's271811', 's25303', 93, 59 from dual union
select 's271813', 's25302', 63, 91 from dual union
select 's271816', 's25301', 90, 83 from dual union
select 's271817', 's25318', 63, 53 from dual

go

select * from stuInfo;
select * from stuMarks;

-- demand ： Create a trigger , Restrict students ： Kangkang forbids inserting 
create or replace trigger t_demo1
after
insert
on stuInfo
for each row
	begin
		-- Restrict Kangkang from inserting 
		if (:new.stuName = ' Kang Kang ') then
			-- Error window prompt , prevent DML Statement runs successfully .raise_application_error( Status code , error message );   Status code range ： -20000  -20099
			raise_application_error('-20001',' Kangkang can't insert , There's a stain ');		
			end if;
		end;

insert into stuInfo
select 's25366', ' Kang Kang 2', ' male ', 18,1, ' Beijing haidian ' from dual;

select * from stuInfo;
rollback;

-- Kang Kang 2 Can't delete 
create or replace trigger t_demo2
after
delete
on stuInfo
for each row
	begin
		if(:old.stuName = ' Kang Kang 2') then
		      raise_application_error('-20002',' Kang Kang 2 Can't delete ');
					end if;
		end;

delete from stuInfo where stuName = ' Kang Kang 2';


-- demand ： To write 1 Trigger , At the same time limit   Kang Kang 2 Can't delete , Mei Chaofeng cannot modify , Liaojiajun can't add 

create or replace trigger t_demo3
after
insert or update or delete
on stuInfo
for each row
begin
	-- A trigger contains multiple limit actions , First judge    Which one triggered ？
	if inserting then
		if (:new.stuName = ' Liaojiajun ') then
			raise_application_error('-20004',' Liaojiajun cannot add ');
		end if;
	elsif deleting then
		if (:old.stuName = ' Kang Kang 2') then
			raise_application_error('-20005',' Kang Kang 2 Can't delete ');
		end if;
  elsif updating then
		if (:old.stuName = ' Mei Chaofeng ') then
			raise_application_error('-20006',' Mei Chaofeng cannot modify ');
		end if;
	end if;
end;
----------------------------------------------------------------
insert into stuInfo
select 's25333', ' Liaojiajun ', ' male ', 18,1, ' Beijing haidian ' from dual;



-- function ： cascading deletion 
select * from stuInfo;
select * from stuMarks;

delete from stuInfo where stuName = ' Zhang Qiuli ';

-- When deleting the data of the main table with a trigger , At the same time, delete the data from the table 
create or replace trigger t_demo4
after
delete
on Stuinfo
for each row
	begin
		-- When the trigger is triggered , Get the table where the trigger is located immediately id   Delete data from the table as a condition 
		delete from stuMarks where stuMarks.Stuno = :old.stuno;
		end;

-- Sequence + trigger    Analog identification column    
drop table new_emp;
create table new_emp
as
select empno,ename,sal from emp where 1= 0;

select * from new_emp;
-- Sequence 
create sequence s_emp; 
-- trigger 
create or replace trigger t_emp
before
insert
on new_emp
for each row
	begin
		-- When the trigger is triggered , Get the next value of the current sequence and assign it to new_emp In the new table id attribute 
		--oracle 10g
		--select s_emp.nextval into :new.empno from dual;
		--oracle 11g
		:new.empno:=s_emp.nextval;
		end;

-- The new data 
insert into new_emp(ename,sal) values(' Zhang San ',2000)
select * from new_emp;




-- Row level triggers and statement level triggers 
create or replace trigger t_emp
after
insert or update or delete
on new_emp
for each row
  begin
    dbms_output.put_line('ok');
    end;
		
create or replace trigger t_emp2
after
insert or update or delete
on new_emp
  begin
    dbms_output.put_line('okok');
    end;
		
		


select * from new_emp;
update new_emp set ename = ' ha-ha ' where ename = ' rees ';