Updating a table using a to_char date

Question

Dear all;
I have the following query and table below
create table t1
       cid varchar2(200),
       yearid varchar2(200),
       begin_date date
insert into t1
           (cid, yearid, begin_date)
         values
           ('A', '2010_1', sysdate);
  insert into t1
           (cid, yearid, begin_date)
         values
           ('B', '2010_1', to_date('03/04/2011', 'MM/DD/YYYY'));
insert into t1
           (cid, yearid, begin_date)
         values
           ('C', '2010_1', to_date('01/02/2011', 'MM/DD/YYYY'));and I have this update statement below
   update t1 t
       set t.yearid = '2011_1'
       where to_char(t.begin_date, 'YYYY') = substr(t.yearid, 1, 4);what i am trying to is basically update table t1 yearid which is a varchar2 where it has to_char begin date that are irregular...so in my sample case,
to_char of the begin date return a 2011
hence, the yearid should be 2011_1 instead.
However, my udate statement isnt working though

Answer 1

Hi,
user13328581 wrote:
Dear all;
I have the following query and table below
create table t1
cid varchar2(200),
yearid varchar2(200),
begin_date date
insert into t1
(cid, yearid, begin_date)
values
('A', '2010_1', sysdate);
insert into t1
(cid, yearid, begin_date)
values
('B', '2010_1', to_date('03/04/2011', 'MM/DD/YYYY'));
insert into t1
(cid, yearid, begin_date)
values
('C', '2010_1', to_date('01/02/2011', 'MM/DD/YYYY'));and I have this update statement below
update t1 t
set t.yearid = '2011_1'
where to_char(t.begin_date, 'YYYY') = substr(t.yearid, 1, 4);what i am trying to is basically update table t1 yearid which is a varchar2 where it has to_char begin date that are irregular...so in my sample case,
to_char of the begin date return a 2011
hence, the yearid should be 2011_1 instead.
However, my udate statement isnt working thoughWhat's wrong with it?
What are the results you want to get (that is, what should the table contain after the UPDATE? Post what you would like to see as the results of "SELECT * FROM t1" after the UPDATE.)
Point out where the UPDATE statement you posted is producing the wrong results.
Is it changing the wrong rows? Maybe the WHERE clause is wrong. Maybe you meant != instead of =.