[sql-server] How to convert Nvarchar column to INT

I have a nvarchar column in one of my tables. Now I need to convert that column values to INT type..

I have tried using

cast(A.my_NvarcharColumn as INT) 

and

convert (int, N'A.my_NvarcharColumn')

When I ran my query I am getting errors like

Conversion failed when converting the nvarchar value ' 23454542 ' to data type int.

hi i am posting my entire code snippet

SELECT A.objID, name, des,  right(Replace(Ltrim(Replace(substring(my_nvarcharcolumn,1,9), '0', ' ')), ' ', '0'),10) AS new_nvarcharcolumn 
INTO #tmp1
FROM [database].[dbo].[tblname] AS A
INNER JOIN (SELECT * FROM [database].[dbo].tblname1 WHERE sourceID = 32) AS AI ON source = A.objID
INNER JOIN [database].[dbo].tblname2 AS I ON I.ObjectID = A.Source

SELECT MAX(m_dAddDate) AS date_Asof, dnum INTO #tmp2 FROM 
(SELECT * FROM [database].[dbo].tblname WHERE senior <> '' AND class = 'SSS') AS A
GROUP BY dnum

SELECT DISTINCT A.* INTO #tmp3 FROM #tmp1 AS A
INNER JOIN #tmp2 AS SD ON SD.dnum =cast(A.new_nvarcharcolumn as INT)
INNER JOIN database.[dbo].tbl4 AS M ON M.dnum = cast(A.new_nvarcharcolumn as INT)  AND SD.date_Asof = M.adddate

You can always use the ISNUMERIC helper function to convert only what's really numeric:

SELECT
     CAST(A.my_NvarcharColumn AS BIGINT)
FROM 
     A
WHERE
     ISNUMERIC(A.my_NvarcharColumn) = 1

Your CAST() looks correct.

Your CONVERT() is not correct. You are quoting the column as a string. You will want something like

CONVERT(INT, A.my_NvarcharColumn)

** notice without the quotes **

The only other reason why this could fail is if you have a non-numeric character in the field value or if it's out of range.

You can try something like the following to verify it's numeric and return a NULL if it's not:

SELECT
 CASE
  WHEN ISNUMERIC(A.my_NvarcharColumn) = 1 THEN CONVERT(INT, A.my_NvarcharColumn)
  ELSE NULL
 END AS my_NvarcharColumn

If you want to convert from char to int, why not think about unicode number?

SELECT UNICODE(';') -- 59

This way you can convert any char to int without any error. Cheers.

CONVERT takes the column name, not a string containing the column name; your current expression tries to convert the string A.my_NvarcharColumn to an integer instead of the column content.

SELECT convert (int, N'A.my_NvarcharColumn') FROM A;

should instead be

SELECT convert (int, A.my_NvarcharColumn) FROM A;

Simple SQLfiddle here.

I know its Too late But I hope it will work new comers Try This Its Working ... :D

select 
  case 
      when isnumeric(my_NvarcharColumn) = 1 then 
              cast(my_NvarcharColumn AS int)
      else
              NULL
 end

AS 'my_NvarcharColumnmitter'
from A