SQL Server converting varchar to INT

Question

I am stuck on converting a varchar column UserID to INT  I know  please don t ask why this UserID column was not created as INT initially  long story   So I tried this  but it doesn t work  and give me an error   select CAST userID AS int  from audit   Error      Conversion failed when converting the varchar value        1581                                                                                                                              to data type int    I did select len userID  from audit and it returns 128 characters  which are not spaces   I tried to detect ASCII characters for those trailing after the ID number and ASCII value   0    I have also tried LTRIM  RTRIM  and replace char 0  with     but does not work     The only way it works when I tell the fixed number of character like this below  but UserID is not always 4 characters    select CAST LEFT userID  4  AS int  from audit

User · Accepted Answer

You could try updating the table to get rid of these characters:

UPDATE dbo.[audit]
  SET UserID = REPLACE(UserID, CHAR(0), '')
  WHERE CHARINDEX(CHAR(0), UserID) > 0;

But then you'll also need to fix whatever is putting this bad data into the table in the first place. In the meantime perhaps try:

SELECT CONVERT(INT, REPLACE(UserID, CHAR(0), ''))
  FROM dbo.[audit];

But that is not a long term solution. Fix the data (and the data type while you're at it). If you can't fix the data type immediately, then you can quickly find the culprit by adding a check constraint:

ALTER TABLE dbo.[audit]
  ADD CONSTRAINT do_not_allow_stupid_data
  CHECK (CHARINDEX(CHAR(0), UserID) = 0);

EDIT

Ok, so that is definitely a 4-digit integer followed by six instances of CHAR(0). And the workaround I posted definitely works for me:

DECLARE @foo TABLE(UserID VARCHAR(32));
INSERT @foo SELECT 0x31353831000000000000;

-- this succeeds:
SELECT CONVERT(INT, REPLACE(UserID, CHAR(0), '')) FROM @foo;

-- this fails:
SELECT CONVERT(INT, UserID) FROM @foo;

Please confirm that this code on its own (well, the first SELECT, anyway) works for you. If it does then the error you are getting is from a different non-numeric character in a different row (and if it doesn't then perhaps you have a build where a particular bug hasn't been fixed). To try and narrow it down you can take random values from the following query and then loop through the characters:

SELECT UserID, CONVERT(VARBINARY(32), UserID)
  FROM dbo.[audit]
  WHERE UserID LIKE '%[^0-9]%';

So take a random row, and then paste the output into a query like this:

DECLARE @x VARCHAR(32), @i INT;
SET @x = CONVERT(VARCHAR(32), 0x...); -- paste the value here
SET @i = 1;
WHILE @i <= LEN(@x)
BEGIN
  PRINT RTRIM(@i) + ' = ' + RTRIM(ASCII(SUBSTRING(@x, @i, 1)))
  SET @i = @i + 1;
END

This may take some trial and error before you encounter a row that fails for some other reason than CHAR(0) - since you can't really filter out the rows that contain CHAR(0) because they could contain CHAR(0) and CHAR(something else). For all we know you have values in the table like:

SELECT '15' + CHAR(9) + '23' + CHAR(0);

...which also can't be converted to an integer, whether you've replaced CHAR(0) or not.

I know you don't want to hear it, but I am really glad this is painful for people, because now they have more war stories to push back when people make very poor decisions about data types.

User · Answer

I would try triming the number to see what you get   select len rtrim ltrim userid    from audit   if that return the correct value then just do   select convert int  rtrim ltrim userid    from audit   if that doesn t return the correct value then I would do a replace to remove the empty space    select convert int  replace userid  char 0        from audit

User · Answer

This is more for someone Searching for a result  than the original post-er  This worked for me     declare  value varchar max     sad   select sum cast iif isnumeric  value    1   value  0  as bigint     returns 0  declare  value varchar max     3   select sum cast iif isnumeric  value    1   value  0  as bigint     returns 3

User · Answer

This question has got 91 000 views so perhaps many people are looking for a more generic solution to the issue in the title  error converting varchar to INT   If you are on SQL Server 2012  one way of handling this invalid data is to use TRY CAST  SELECT TRY CAST  userID AS INT  FROM   audit    On previous versions you could use  SELECT CASE          WHEN ISNUMERIC RTRIM userID      0e0     1               AND LEN userID   lt   11            THEN CAST userID AS INT         END FROM   audit    Both return NULL if the value cannot be cast   In the specific case that you have in your question with known bad values I would use the following however   CAST REPLACE userID COLLATE Latin1 General Bin  CHAR 0      AS INT    Trying to replace the null character is often problematic except if using a binary collation

[sql-server] SQL Server : converting varchar to INT

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