Find non-ASCII characters in varchar columns using SQL Server

Here is a solution for the single column search using PATINDEX.
It also displays the StartPosition, InvalidCharacter and ASCII code.

select line,
  patindex('%[^ !-~]%' COLLATE Latin1_General_BIN,Line) as [Position],
  substring(line,patindex('%[^ !-~]%' COLLATE Latin1_General_BIN,Line),1) as [InvalidCharacter],
  ascii(substring(line,patindex('%[^ !-~]%' COLLATE Latin1_General_BIN,Line),1)) as [ASCIICode]
from  staging.APARMRE1
where patindex('%[^ !-~]%' COLLATE Latin1_General_BIN,Line) >0

try something like this:

DECLARE @YourTable table (PK int, col1 varchar(20), col2 varchar(20), col3 varchar(20));
INSERT @YourTable VALUES (1, 'ok','ok','ok');
INSERT @YourTable VALUES (2, 'BA'+char(182)+'D','ok','ok');
INSERT @YourTable VALUES (3, 'ok',char(182)+'BAD','ok');
INSERT @YourTable VALUES (4, 'ok','ok','B'+char(182)+'AD');
INSERT @YourTable VALUES (5, char(182)+'BAD','ok',char(182)+'BAD');
INSERT @YourTable VALUES (6, 'BAD'+char(182),'B'+char(182)+'AD','BAD'+char(182)+char(182)+char(182));

--if you have a Numbers table use that, other wise make one using a CTE
WITH AllNumbers AS
(   SELECT 1 AS Number
    UNION ALL
    SELECT Number+1
        FROM AllNumbers
        WHERE Number<1000
)
SELECT 
    pk, 'Col1' BadValueColumn, CONVERT(varchar(20),col1) AS BadValue --make the XYZ in convert(varchar(XYZ), ...) the largest value of col1, col2, col3
    FROM @YourTable           y
        INNER JOIN AllNumbers n ON n.Number <= LEN(y.col1)
    WHERE ASCII(SUBSTRING(y.col1, n.Number, 1))<32 OR ASCII(SUBSTRING(y.col1, n.Number, 1))>127
UNION
SELECT 
    pk, 'Col2' BadValueColumn, CONVERT(varchar(20),col2) AS BadValue --make the XYZ in convert(varchar(XYZ), ...) the largest value of col1, col2, col3
    FROM @YourTable           y
        INNER JOIN AllNumbers n ON n.Number <= LEN(y.col2)
    WHERE ASCII(SUBSTRING(y.col2, n.Number, 1))<32 OR ASCII(SUBSTRING(y.col2, n.Number, 1))>127
UNION
SELECT 
    pk, 'Col3' BadValueColumn, CONVERT(varchar(20),col3) AS BadValue --make the XYZ in convert(varchar(XYZ), ...) the largest value of col1, col2, col3
    FROM @YourTable           y
        INNER JOIN AllNumbers n ON n.Number <= LEN(y.col3)
    WHERE ASCII(SUBSTRING(y.col3, n.Number, 1))<32 OR ASCII(SUBSTRING(y.col3, n.Number, 1))>127
order by 1
OPTION (MAXRECURSION 1000);

OUTPUT:

pk          BadValueColumn BadValue
----------- -------------- --------------------
2           Col1           BA¶D
3           Col2           ¶BAD
4           Col3           B¶AD
5           Col1           ¶BAD
5           Col3           ¶BAD
6           Col1           BAD¶
6           Col2           B¶AD
6           Col3           BAD¶¶¶

(8 row(s) affected)

I've been running this bit of code with success

declare @UnicodeData table (
     data nvarchar(500)
)
insert into 
    @UnicodeData
values 
    (N'Horse�')
    ,(N'Dog')
    ,(N'Cat')

select
    data
from
    @UnicodeData 
where
    data collate LATIN1_GENERAL_BIN != cast(data as varchar(max))

Which works well for known columns.

For extra credit, I wrote this quick script to search all nvarchar columns in a given table for Unicode characters.

declare 
    @sql    varchar(max)    = ''
    ,@table sysname         = 'mytable' -- enter your table here

;with ColumnData as (
    select
        RowId               = row_number() over (order by c.COLUMN_NAME)
        ,c.COLUMN_NAME
        ,ColumnName         = '[' + c.COLUMN_NAME + ']'
        ,TableName          = '[' + c.TABLE_SCHEMA + '].[' + c.TABLE_NAME + ']' 
    from
        INFORMATION_SCHEMA.COLUMNS c
    where
        c.DATA_TYPE         = 'nvarchar'
        and c.TABLE_NAME    = @table
)
select
    @sql = @sql + 'select FieldName = ''' + c.ColumnName + ''',         InvalidCharacter = [' + c.COLUMN_NAME + ']  from ' + c.TableName + ' where ' + c.ColumnName + ' collate LATIN1_GENERAL_BIN != cast(' + c.ColumnName + ' as varchar(max)) '  +  case when c.RowId <> (select max(RowId) from ColumnData) then  ' union all ' else '' end + char(13)
from
    ColumnData c

-- check
-- print @sql
exec (@sql)

I'm not a fan of dynamic SQL but it does have its uses for exploratory queries like this.

This script searches for non-ascii characters in one column. It generates a string of all valid characters, here code point 32 to 127. Then it searches for rows that don't match the list:

declare @str varchar(128);
declare @i int;
set @str = '';
set @i = 32;
while @i <= 127
    begin
    set @str = @str + '|' + char(@i);
    set @i = @i + 1;
    end;

select  col1
from    YourTable
where   col1 like '%[^' + @str + ']%' escape '|';

running the various solutions on some real world data - 12M rows varchar length ~30, around 9k dodgy rows, no full text index in play, the patIndex solution is the fastest, and it also selects the most rows.

(pre-ran km. to set the cache to a known state, ran the 3 processes, and finally ran km again - the last 2 runs of km gave times within 2 seconds)

patindex solution by Gerhard Weiss -- Runtime 0:38, returns 9144 rows

select dodgyColumn from myTable fcc
WHERE  patindex('%[^ !-~]%' COLLATE Latin1_General_BIN,dodgyColumn ) >0

the substring-numbers solution by MT. -- Runtime 1:16, returned 8996 rows

select dodgyColumn from myTable fcc
INNER JOIN dbo.Numbers32k dn ON dn.number<(len(fcc.dodgyColumn ))
WHERE ASCII(SUBSTRING(fcc.dodgyColumn , dn.Number, 1))<32 
    OR ASCII(SUBSTRING(fcc.dodgyColumn , dn.Number, 1))>127

udf solution by Deon Robertson -- Runtime 3:47, returns 7316 rows

select dodgyColumn 
from myTable 
where dbo.udf_test_ContainsNonASCIIChars(dodgyColumn , 1) = 1