识别 SQL 中的特殊字符和数字

Question

In my case, I have a varchar variable like Test1@abc . I want to identify the special characters and numbers in that string and return them. This string can only include alphabetic letters, space, and underscore (az, AZ, space,_). All other characters are not allowed. I want to return them. Thank you.

DECLARE @StringVal VARCHAR(250) = 'Test1@abc' 
IF(--condition)
BEGIN
    --output -> 1,@
END

Answer 1

Using Regex

DECLARE @StringVal VARCHAR(400) = 'Test1@abc'

DECLARE @expres VARCHAR(50) = '%[^~,@,#,$,%,&,*,(,),.,!,0-9]%'

WHILE PATINDEX( @expres, @StringVal ) > 0
SET @StringVal = Replace(REPLACE( @StringVal, SUBSTRING( @StringVal, PATINDEX( @expres, @StringVal ), 1 ),''),'-',' ')

IF(@StringVal LIKE '%[~,@,#,$,%,&,*,(,),.,!,0-9]%')
BEGIN
SELECT @StringVal AS [Special Char]
END
ELSE
SELECT 'No Special Characters'  AS [Non Special Char]

Answer 2

If you want the results just printed out, you can use:

DECLARE @StringVal VARCHAR(400) = 'Test1@abc';  
DECLARE @expres VARCHAR(MAX) = '%[^a-zA-Z_]%';

WHILE @StringVal LIKE @expres
BEGIN
    PRINT SUBSTRING(@stringVal, PATINDEX(@expres, @stringVal), 1);
    SET @stringval = STUFF(@stringVal, 1, PATINDEX(@expres, @stringVal), '');
END;

If you want them output as a string, you can concatenate them:

DECLARE @StringVal VARCHAR(400) = 'Test1@abc';
DECLARE @expres VARCHAR(MAX) = '%[^a-zA-Z_]%';
DECLARE @output VARCHAR(MAX) = '';

WHILE @StringVal LIKE @expres
BEGIN
    SET @output = @output + SUBSTRING(@stringVal, PATINDEX(@expres, @stringVal), 1);
    SET @stringval = STUFF(@stringVal, 1, PATINDEX(@expres, @stringVal), '');
END;

SELECT @output;

Here is a db<>fiddle.