當使用者a,b存放資料到tablec的時候，會將使用者a插入的資料的主鍵值和使用者名稱一起存放到tabled去
即tablec（id(pk),name,pass）a使用者插入（23，『a1』，『a2』）b使用者插入（20，『b1』，『b2』）
觸發器的作用是將（23，a）插入到表tabled去
mysql：
delimiter $$ --宣告結束符號為「$$」
create trigger insert_user_t_trigger before insert on user_t
for each row
begin
declare keyfieldname varchar(50) ;
declare login_name varchar(50);
select column_name into keyfieldname from information_schema.key_column_usage
where table_name='user_t';
select user() into login_name ;
if (keyfieldname ='id' and login_name= 'root@localhost' ) then
insert into u_t(key_id,key_name) values(new.id,login_name);
elseif ( keyfieldname ='username' and login_name= 'root@localhost' ) then
insert into u_t(key_id,key_name) values(new.username,login_name);
else
insert into u_t(key_id,key_name) values(new.password,login_name);
end if;
end $$
oracle:
create or replace trigger insert_user_t_trigger
after insert on user_t
for each row
declare
v_sql varchar2(1000) ;
keyfieldname varchar2(50) ;
login_name varchar2(50) ;
begin
select c.column_name into keyfieldname from user_cons_columns c where c.table_name ='user_t' and c.position is not null and rownum = 1;
select user into login_name from dual where rownum=1;
if inserting and keyfieldname ='id' and login_name= 'scott' then
insert into u_t(key_id,key_name) values(:new.id,login_name);
elsif inserting and keyfieldname ='username' and login_name= 'scott' then
insert into u_t(key_id,key_name) values(:new.username,login_name);
elsif inserting and keyfieldname ='password' and login_name= 'scott' then
insert into u_t(key_id,key_name) values(:new.password,login_name);
end if;
end insert_user_t_trigger;
sqlserver:
create trigger insert_user_t_trigger on user_t
for insert
asdeclare @keyfieldname varchar(50) ,@login_name varchar(50),@id varchar(50),@username varchar(50),@password varchar(50);
select @keyfieldname=column_name from information_schema.key_column_usage
where table_name='user_t';
select @login_name= suser_name() ;
if (@keyfieldname ='id' and @login_name= 'sa' )
begin
select @id=id from inserted;
insert into u_t(key_id,key_name) values(@id,@login_name);
endelse if( @keyfieldname ='username' and @login_name= 'sa' )
begin
select @username=username from inserted;
insert into u_t(key_id,key_name) values(@username,@login_name);
endelse
begin
select @password=password from inserted;
insert into u_t(key_id,key_name) values(@password,@login_name);
end;
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