How to check for Non-Ascii Characters

Question

What is the best way to check if a VARCHAR field has Non-Ascii Characters?
CHAR(1) through CHAR(31) and CHAR(127) through CHAR(255).

I tried using PATINDEX and have run into the following issue.

Checking the lower range worked correctly.

SELECT *      
FROM mbrnotes      
WHERE PATINDEX('%[' + CHAR(1)+ '-' +CHAR(31)+']%',LINE_TEXT) > 0  

My data had three records with 0x1E and all three where returned.

But when I check just the upper range:

SELECT *      
FROM mbrnotes      
WHERE PATINDEX('%[' + CHAR(127)+ '-' +CHAR(255)+']%',LINE_TEXT) > 0 

It returns close to all the records in the table (table count 170737 and returned count 170735) and since my data did not have any values in this range I would think it should have returned no records.

Answer 1

Ranges in the pattern syntax use the sorting rules of your collation.

Use a binary collate clause so the range is ordered by character code.

(I also changed it to LIKE as I find that more obvious than PATINDEX > 0)

SELECT *
FROM mbrnotes
WHERE LINE_TEXT COLLATE Latin1_General_100_BIN2 
     LIKE '%[' + CHAR(0)+ '-' +CHAR(31) + CHAR(127)+ '-' +CHAR(255)+']%'  

If you actually want to see the offending characters and you are on a version with the TRANSLATE function you can use something like the below

DECLARE @WhiteListedCharacters NVARCHAR(1000)
= ' !"#$%&''()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+ '[\]^_`abcdefghijklmnopqrstuvwxyz{|}~'

SELECT text,
    REPLACE(
        TRANSLATE(
            text,
            @WhiteListedCharacters COLLATE Latin1_General_100_BIN2, 
            REPLICATE(
                LEFT(@WhiteListedCharacters,1),
                LEN(@WhiteListedCharacters))), 
        LEFT(@WhiteListedCharacters,1), 
        '') AS BadChars
FROM   sys.messages
WHERE  language_id = 1038 

You can then use that result in a second call to TRANSLATE to preserve only the "good" characters.

DECLARE @WhiteListedCharacters NVARCHAR(1000)
= ' !"#$%&''()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+ '[\]^_`abcdefghijklmnopqrstuvwxyz{|}~'

SELECT text,
    BadChars,
    Cleaned = REPLACE(
                  TRANSLATE(
                      text  COLLATE Latin1_General_100_BIN2,
                      BadChars,
                      REPLICATE(N'ψ', LEN(BadChars))
                      ),
              N'ψ', N'')
FROM sys.messages
CROSS APPLY
(
SELECT REPLACE(
           TRANSLATE(
               text,
               @WhiteListedCharacters COLLATE Latin1_General_100_BIN2,
               REPLICATE(
                   LEFT(@WhiteListedCharacters,1),
                   LEN(@WhiteListedCharacters + '-') - 1)),
               LEFT(@WhiteListedCharacters,1), 
        '') AS BadChars
) ca
WHERE language_id = 1038

Answer 2

If you're like me and you've gotten tired over the years searching for these characters in your company's terrible data, you can use this function or rewrite it for your own purpose. It's admittedly wordy, but it goes the extra step of identifying special characters if you want - uncomment lines 19 - 179 to do so.

If the string does not contain non-printable or extended ascii values - it returns NULL.

CREATE FUNCTION [dbo].[Find_Invalid_Chars]
(
    @SearchString VARCHAR(8000)
)
RETURNS VARCHAR(8000)
AS
BEGIN
    DECLARE @CharPosition INT, @CharVal VARCHAR(100), @ReturnVal VARCHAR(8000) = '', @isValid BIT = 1 -- Start as valid

    SET @CharPosition = 1

    WHILE @CharPosition <= DATALENGTH(@SearchString)
    BEGIN
    IF (ASCII(SUBSTRING(@SearchString, @CharPosition, 1)) NOT BETWEEN (32) AND (127))
        BEGIN
            SET @CharVal = '[' + CAST(ASCII(SUBSTRING(@SearchString, @CharPosition, 1)) AS VARCHAR(3)) + ']'
            SET @isValid = 0
            ---- Non-Printables
            --SET @CharVal = REPLACE(@CharVal, '[0]', '[NUL]')
            --SET @CharVal = REPLACE(@CharVal, '[1]', '[SOH]')
            --SET @CharVal = REPLACE(@CharVal, '[2]', '[STX]')
            --SET @CharVal = REPLACE(@CharVal, '[3]', '[ETX]')
            --SET @CharVal = REPLACE(@CharVal, '[4]', '[EOT]')
            --SET @CharVal = REPLACE(@CharVal, '[5]', '[ENQ]')
            --SET @CharVal = REPLACE(@CharVal, '[6]', '[ACK]')
            --SET @CharVal = REPLACE(@CharVal, '[7]', '[BEL]')
            --SET @CharVal = REPLACE(@CharVal, '[8]', '[BS]')
            --SET @CharVal = REPLACE(@CharVal, '[9]', '[HT]')
            --SET @CharVal = REPLACE(@CharVal, '[10]', '[LF]')
            --SET @CharVal = REPLACE(@CharVal, '[11]', '[VT]')
            --SET @CharVal = REPLACE(@CharVal, '[12]', '[FF]')
            --SET @CharVal = REPLACE(@CharVal, '[13]', '[CR]')
            --SET @CharVal = REPLACE(@CharVal, '[14]', '[SO]')
            --SET @CharVal = REPLACE(@CharVal, '[15]', '[SI]')
            --SET @CharVal = REPLACE(@CharVal, '[16]', '[DLE]')
            --SET @CharVal = REPLACE(@CharVal, '[17]', '[DC1]')
            --SET @CharVal = REPLACE(@CharVal, '[18]', '[DC2]')
            --SET @CharVal = REPLACE(@CharVal, '[19]', '[DC3]')
            --SET @CharVal = REPLACE(@CharVal, '[20]', '[DC4]')
            --SET @CharVal = REPLACE(@CharVal, '[21]', '[NAK]')
            --SET @CharVal = REPLACE(@CharVal, '[22]', '[SYN]')
            --SET @CharVal = REPLACE(@CharVal, '[23]', '[ETB]')
            --SET @CharVal = REPLACE(@CharVal, '[24]', '[CAN]')
            --SET @CharVal = REPLACE(@CharVal, '[25]', '[EM]')
            --SET @CharVal = REPLACE(@CharVal, '[26]', '[SUB]')
            --SET @CharVal = REPLACE(@CharVal, '[27]', '[ESC]')
            --SET @CharVal = REPLACE(@CharVal, '[28]', '[FS]')
            --SET @CharVal = REPLACE(@CharVal, '[29]', '[GS]')
            --SET @CharVal = REPLACE(@CharVal, '[30]', '[RS]')
            --SET @CharVal = REPLACE(@CharVal, '[31]', '[US]')
            ---- Extended Ascii
            --SET @CharVal = REPLACE(@CharVal, '[128]', '[€]')
            --SET @CharVal = REPLACE(@CharVal, '[129]', '[]]')
            --SET @CharVal = REPLACE(@CharVal, '[130]', '[‚]')
            --SET @CharVal = REPLACE(@CharVal, '[131]', '[ƒ]')
            --SET @CharVal = REPLACE(@CharVal, '[132]', '[„]')
            --SET @CharVal = REPLACE(@CharVal, '[133]', '[…]')
            --SET @CharVal = REPLACE(@CharVal, '[134]', '[†]')
            --SET @CharVal = REPLACE(@CharVal, '[135]', '[‡]')
            --SET @CharVal = REPLACE(@CharVal, '[136]', '[ˆ]')
            --SET @CharVal = REPLACE(@CharVal, '[137]', '[‰]')
            --SET @CharVal = REPLACE(@CharVal, '[138]', '[Š]')
            --SET @CharVal = REPLACE(@CharVal, '[139]', '[‹]')
            --SET @CharVal = REPLACE(@CharVal, '[140]', '[Œ]')
            --SET @CharVal = REPLACE(@CharVal, '[141]', '[]]')
            --SET @CharVal = REPLACE(@CharVal, '[142]', '[Ž]')
            --SET @CharVal = REPLACE(@CharVal, '[143]', '[]]')
            --SET @CharVal = REPLACE(@CharVal, '[144]', '[]]')
            --SET @CharVal = REPLACE(@CharVal, '[145]', '[‘]')
            --SET @CharVal = REPLACE(@CharVal, '[146]', '[’]')
            --SET @CharVal = REPLACE(@CharVal, '[147]', '[“]')
            --SET @CharVal = REPLACE(@CharVal, '[148]', '[”]')
            --SET @CharVal = REPLACE(@CharVal, '[149]', '[•]')
            --SET @CharVal = REPLACE(@CharVal, '[150]', '[–]')
            --SET @CharVal = REPLACE(@CharVal, '[151]', '[—]')
            --SET @CharVal = REPLACE(@CharVal, '[152]', '[˜]')
            --SET @CharVal = REPLACE(@CharVal, '[153]', '[™]')
            --SET @CharVal = REPLACE(@CharVal, '[154]', '[š]')
            --SET @CharVal = REPLACE(@CharVal, '[155]', '[›]')
            --SET @CharVal = REPLACE(@CharVal, '[156]', '[œ]')
            --SET @CharVal = REPLACE(@CharVal, '[157]', '[]]')
            --SET @CharVal = REPLACE(@CharVal, '[158]', '[ž]')
            --SET @CharVal = REPLACE(@CharVal, '[159]', '[Ÿ]')
            --SET @CharVal = REPLACE(@CharVal, '[160]', '[]]')
            --SET @CharVal = REPLACE(@CharVal, '[161]', '[¡]')
            --SET @CharVal = REPLACE(@CharVal, '[162]', '[¢]')
            --SET @CharVal = REPLACE(@CharVal, '[163]', '[£]')
            --SET @CharVal = REPLACE(@CharVal, '[164]', '[¤]')
            --SET @CharVal = REPLACE(@CharVal, '[165]', '[¥]')
            --SET @CharVal = REPLACE(@CharVal, '[166]', '[¦]')
            --SET @CharVal = REPLACE(@CharVal, '[167]', '[§]')
            --SET @CharVal = REPLACE(@CharVal, '[168]', '[¨]')
            --SET @CharVal = REPLACE(@CharVal, '[169]', '[©]')
            --SET @CharVal = REPLACE(@CharVal, '[170]', '[ª]')
            --SET @CharVal = REPLACE(@CharVal, '[171]', '[«]')
            --SET @CharVal = REPLACE(@CharVal, '[172]', '[¬]')
            --SET @CharVal = REPLACE(@CharVal, '[173]', '[]]')
            --SET @CharVal = REPLACE(@CharVal, '[174]', '[®]')
            --SET @CharVal = REPLACE(@CharVal, '[175]', '[¯]')
            --SET @CharVal = REPLACE(@CharVal, '[176]', '[°]')
            --SET @CharVal = REPLACE(@CharVal, '[177]', '[±]')
            --SET @CharVal = REPLACE(@CharVal, '[178]', '[²]')
            --SET @CharVal = REPLACE(@CharVal, '[179]', '[³]')
            --SET @CharVal = REPLACE(@CharVal, '[180]', '[´]')
            --SET @CharVal = REPLACE(@CharVal, '[181]', '[µ]')
            --SET @CharVal = REPLACE(@CharVal, '[182]', '[¶]')
            --SET @CharVal = REPLACE(@CharVal, '[183]', '[·]')
            --SET @CharVal = REPLACE(@CharVal, '[184]', '[¸]')
            --SET @CharVal = REPLACE(@CharVal, '[185]', '[¹]')
            --SET @CharVal = REPLACE(@CharVal, '[186]', '[º]')
            --SET @CharVal = REPLACE(@CharVal, '[187]', '[»]')
            --SET @CharVal = REPLACE(@CharVal, '[188]', '[¼]')
            --SET @CharVal = REPLACE(@CharVal, '[189]', '[½]')
            --SET @CharVal = REPLACE(@CharVal, '[190]', '[¾]')
            --SET @CharVal = REPLACE(@CharVal, '[191]', '[¿]')
            --SET @CharVal = REPLACE(@CharVal, '[192]', '[À]')
            --SET @CharVal = REPLACE(@CharVal, '[193]', '[Á]')
            --SET @CharVal = REPLACE(@CharVal, '[194]', '[Â]')
            --SET @CharVal = REPLACE(@CharVal, '[195]', '[Ã]')
            --SET @CharVal = REPLACE(@CharVal, '[196]', '[Ä]')
            --SET @CharVal = REPLACE(@CharVal, '[197]', '[Å]')
            --SET @CharVal = REPLACE(@CharVal, '[198]', '[Æ]')
            --SET @CharVal = REPLACE(@CharVal, '[199]', '[Ç]')
            --SET @CharVal = REPLACE(@CharVal, '[200]', '[È]')
            --SET @CharVal = REPLACE(@CharVal, '[201]', '[É]')
            --SET @CharVal = REPLACE(@CharVal, '[202]', '[Ê]')
            --SET @CharVal = REPLACE(@CharVal, '[203]', '[Ë]')
            --SET @CharVal = REPLACE(@CharVal, '[204]', '[Ì]')
            --SET @CharVal = REPLACE(@CharVal, '[205]', '[Í]')
            --SET @CharVal = REPLACE(@CharVal, '[206]', '[Î]')
            --SET @CharVal = REPLACE(@CharVal, '[207]', '[Ï]')
            --SET @CharVal = REPLACE(@CharVal, '[208]', '[Ð]')
            --SET @CharVal = REPLACE(@CharVal, '[209]', '[Ñ]')
            --SET @CharVal = REPLACE(@CharVal, '[210]', '[Ò]')
            --SET @CharVal = REPLACE(@CharVal, '[211]', '[Ó]')
            --SET @CharVal = REPLACE(@CharVal, '[212]', '[Ô]')
            --SET @CharVal = REPLACE(@CharVal, '[213]', '[Õ]')
            --SET @CharVal = REPLACE(@CharVal, '[214]', '[Ö]')
            --SET @CharVal = REPLACE(@CharVal, '[215]', '[×]')
            --SET @CharVal = REPLACE(@CharVal, '[216]', '[Ø]')
            --SET @CharVal = REPLACE(@CharVal, '[217]', '[Ù]')
            --SET @CharVal = REPLACE(@CharVal, '[218]', '[Ú]')
            --SET @CharVal = REPLACE(@CharVal, '[219]', '[Û]')
            --SET @CharVal = REPLACE(@CharVal, '[220]', '[Ü]')
            --SET @CharVal = REPLACE(@CharVal, '[221]', '[Ý]')
            --SET @CharVal = REPLACE(@CharVal, '[222]', '[Þ]')
            --SET @CharVal = REPLACE(@CharVal, '[223]', '[ß]')
            --SET @CharVal = REPLACE(@CharVal, '[224]', '[à]')
            --SET @CharVal = REPLACE(@CharVal, '[225]', '[á]')
            --SET @CharVal = REPLACE(@CharVal, '[226]', '[â]')
            --SET @CharVal = REPLACE(@CharVal, '[227]', '[ã]')
            --SET @CharVal = REPLACE(@CharVal, '[228]', '[ä]')
            --SET @CharVal = REPLACE(@CharVal, '[229]', '[å]')
            --SET @CharVal = REPLACE(@CharVal, '[230]', '[æ]')
            --SET @CharVal = REPLACE(@CharVal, '[231]', '[ç]')
            --SET @CharVal = REPLACE(@CharVal, '[232]', '[è]')
            --SET @CharVal = REPLACE(@CharVal, '[233]', '[é]')
            --SET @CharVal = REPLACE(@CharVal, '[234]', '[ê]')
            --SET @CharVal = REPLACE(@CharVal, '[235]', '[ë]')
            --SET @CharVal = REPLACE(@CharVal, '[236]', '[ì]')
            --SET @CharVal = REPLACE(@CharVal, '[237]', '[í]')
            --SET @CharVal = REPLACE(@CharVal, '[238]', '[î]')
            --SET @CharVal = REPLACE(@CharVal, '[239]', '[ï]')
            --SET @CharVal = REPLACE(@CharVal, '[240]', '[ð]')
            --SET @CharVal = REPLACE(@CharVal, '[241]', '[ñ]')
            --SET @CharVal = REPLACE(@CharVal, '[242]', '[ò]')
            --SET @CharVal = REPLACE(@CharVal, '[243]', '[ó]')
            --SET @CharVal = REPLACE(@CharVal, '[244]', '[ô]')
            --SET @CharVal = REPLACE(@CharVal, '[245]', '[õ]')
            --SET @CharVal = REPLACE(@CharVal, '[246]', '[ö]')
            --SET @CharVal = REPLACE(@CharVal, '[247]', '[÷]')
            --SET @CharVal = REPLACE(@CharVal, '[248]', '[ø]')
            --SET @CharVal = REPLACE(@CharVal, '[249]', '[ù]')
            --SET @CharVal = REPLACE(@CharVal, '[250]', '[ú]')
            --SET @CharVal = REPLACE(@CharVal, '[251]', '[û]')
            --SET @CharVal = REPLACE(@CharVal, '[252]', '[ü]')
            --SET @CharVal = REPLACE(@CharVal, '[253]', '[ý]')
            --SET @CharVal = REPLACE(@CharVal, '[254]', '[þ]')
            --SET @CharVal = REPLACE(@CharVal, '[255]', '[ÿ]')
        END
    ELSE
        BEGIN
            SET @CharVal = SUBSTRING(@SearchString, @CharPosition, 1)
        END

    SET @ReturnVal = @ReturnVal + @CharVal

    SET @CharPosition = @CharPosition + 1
    END

IF (@isValid = 1) SET @ReturnVal = NULL

RETURN @ReturnVal

END

And then, call it like:

SELECT BadString, dbo.Find_Invalid_Chars(BadString) [Invalid Characters]
FROM #tmp_Table tmp_mc
WHERE dbo.Find_Invalid_Chars(BadString) IS NOT NULL

Sample Output:

Or