Create trigger to insert a column value into other column of same table SQL Server 2005 -

how create trigger insert value in column same value of column of same table of newly inserted row in table.

suppose have table below

columna | columnb 

i want columnb value inserted columna row gets inserted table or columnb value gets updated . should not vice versa ie insert columna value columnb

.below code handles insert , please me how handle both insertion , updation of table ie when columnb value gets inserted or updated.

create trigger inserupdate    on  triggertesttable    after insert,update  begin     -- set nocount on added prevent result sets     -- interfering select statements.     set nocount on;      -- insert statements trigger here     declare @value int      select @value=columnb inserted      update triggertesttable     set columna=@value  end go 

this works fine if values inserted below

insert triggertesttable(columnb) values('xyz') 

columnb value gets inserted columna

columna | columnb   xyz   |  xyz  

but null value gets updated in both if other application inserts value in columna

 insert triggertesttable(columna) values('pqr') 

now records are

columna | columnb   xyz   |  xyz    null  |  null 

the correct recordset should below

  columna   | columnb       xyz   |  xyz        pqr   |  null 

how solve problem.

try trigger (it copy values columnb columna when inserted values columnb or when updated values columbb):

create trigger trgiu_triggertesttable_updatecolumnawhencolumnb    on  dbo.triggertesttable    after insert,update  begin     -- set nocount on added prevent result sets     -- interfering select statements.     set nocount on;      if update(columnb)     begin         update  dbo.triggertesttable         set     columna=i.columnb            inserted         inner join dbo.triggertesttable t on i.myid=t.myid         left join deleted d on i.myid=d.myid           d.myid null , i.columnb not null -- row inserted         or      d.myid not null -- row updated     end end go 

i used table:

create table dbo.triggertesttable(     myid int identity(1,1) primary key, -- myid should primary key or mandatory(not null) unique constraint     columna varchar(100),     columnb varchar(100) ); go