SQL ASP.NET-将nvarchar转换为int（如果为数字）

Question

I have an nvarchar field called [DBO] which contains either a numeric age (like 32) or other nvarchar valuesl ike Unknown or 12/10/2013

What I'm trying to achieve is to convert [DBO] to int if it's numeric. This is the code I currently have, but it's obviously not working.

SELECT * FROM [PeopleTable] WHERE CAST([DBO] AS INT)=32

It always gives me an error for [DBO]'s value not being an int. I was trying to use "CASE" but I can't see how to implement that in my command.

Answer 1

You should be able to pull all records that are numeric only and then do your cast.

SELECT * 
FROM [PeopleTable] P
WHERE CAST(P.[DBO] AS INT) = 32
AND ISNUMERIC(P.[DBO]) = 1

Answer 2

Have a look here: TRY_PARSE function (for SQL Server 2012 and newer)

And here: ISNUMERIC function for SQL Server 2005 and newer

Answer 3

Try this:

SELECT * FROM [PeopleTable] P
WHERE ISNUMERIC(P.[DBO]) = 1) AND CAST(P.[DBO] AS INT) = 32

Answer 4

I would use

select 
    convert(int,[dbo])
from @t
where not ([dbo] like '%[^0-9]%')

If you use ISNUMERIC , you'll get an error if you have a decimal value in your data.

Answer 5

SELECT * FROM
            (
            SELECT *,
              CAST((CASE isnumeric(ColumnName) 
                      WHEN 0 THEN NULL 
                      ELSE CAST(ColumnName AS DECIMAL(10, 2)) 
                    END) AS INT) AS ColumnName1 
            FROM tablename
            ) T
WHERE ColumnName1 = yourNumber