SQL Convert Nvarchar(255) to DateTime problem

Question

I'm using SQL server 2008.

I have 2 Tables: Table 1 and Table 2.

Table 1 has 1 column called: OldDate which is nvarchar(255), null
Table 2 has 1 column called: NewDate which is datetime, not null

Example data in Table 1:

26/07/03
NULL
NULL
23/07/2003
7/26/2003
NULL
28/07/03

When i try CAST(OldDate as datetime)

I get this error:

Arithmetic overflow error converting expression to data type datetime.

I need to insert OldDate into NewDate with no errors. I can't skip some rows.

Answer 1

try using

CONVERT(datetime,OldDate ,103)

the "103" tells the converter that the format is dd/mm/yyyy

EDIT

here is a good like with many examples: http://www.sqlusa.com/bestpractices/datetimeconversion/

You seem to have m/d/y as well as d/m/y data, this is about the best you can do:

DECLARE @Table1 table (PK int, OldDate nvarchar(255) null)
DECLARE @Table2 table (PK int, NewDate datetime not null)
INSERT @Table1 VALUES (1,'26/07/03')
INSERT @Table1 VALUES (2,null)
INSERT @Table1 VALUES (3,null)
INSERT @Table1 VALUES (4,'23/07/2003')
INSERT @Table1 VALUES (5,'7/26/2003')
INSERT @Table1 VALUES (6,null)
INSERT @Table1 VALUES (7,'28/07/03')

SET DATEFORMAT dmy

INSERT INTO @Table2
        (PK, NewDate)
    SELECT
        PK,
        CASE 
            WHEN ISDATE(OldDate)=1 THEN OldDate
            ELSE '1/1/1900'
        END
        FROM @Table1

SET DATEFORMAT mdy

UPDATE t2
    SET NewDate=OldDate
    FROM @Table2           t2
        INNER JOIN @Table1 t1 ON t2.PK=t1.PK
    WHERE t2.NewDate='1/1/1900' AND ISDATE(OldDate)=1 

SELECT * FROM @Table2

OUTPUT:

PK          NewDate
----------- -----------------------
1           2003-07-26 00:00:00.000
2           1900-01-01 00:00:00.000
3           1900-01-01 00:00:00.000
4           2003-07-23 00:00:00.000
5           2003-07-26 00:00:00.000
6           1900-01-01 00:00:00.000
7           2003-07-28 00:00:00.000

(7 row(s) affected)

I used '1/1/1900' because you have NewDate as NOT NULL.

Answer 2

It seems you have incorrect data (or a typo).

Some of dates are in British/French standard dd/mm/yyyy(see code 103) and some in USA standard mm/dd/yyyy(code 101).

For the first case you could try CONVERT(datetime, [OldDate], 103),

for the second CONVERT(datetime, [OldDate], 101)