Question

I have about 2 million rows in my table with a column for dates… this column is of type VARCHAR, and it contains a wrong date format, we have this format dd/mm/YYYY and it must be YYYY-mm-dd…

How can I change it? Remember it is a Varchar column, not a Datetime column (and it can’t be datetime field because we manipulate it with our queries)

Thank you in advice.

UPDATE

As I said, I have MILLIONS of rows, so it’s not possible to query one by one the date field to a new one, as you said in your responses…. I need some kind of “automatic” mode to transfer every row to it’s new format and datatype column.

Answer 1

If your end goal is just cleanup to end up in a datetime column, you only need to add a new column, then transfer the data:

update tbl
   set new_datetime_col = convert(datetime, dateinvarchar, 103);

---

Query:

update tbl
   set dateinvarchar = convert(char(10),
                       convert(datetime,
                               dateinvarchar, 103), 121)
select * from tbl

Sample table:

create table tbl (dateinvarchar varchar(10));
insert tbl values
  ('01/02/2012'),
  ('02/02/2012'),
  ('03/02/2012'),
  ('14/12/2012');

Sample Result:

| DATEINVARCHAR |
-----------------
|    2012-02-01 |
|    2012-02-02 |
|    2012-02-03 |
|    2012-12-14 |