Inserting special characters inside a string without replacing any character - sql

Question

Suppose I have a varchar variable.Can I insert different symbols after evry 2 character of the string untill end of the string .i.e untill length (string).
For example:
Input: '12345678'
And we don't know what is input and length of input and the output we want is :
Output: '12_34&56#78' (special character can be anything )
Please let me know if it possible doing dynamically using loop or something.

Answer 1

This can be done using a simple REGEXP_REPLACE.
The first argument will be your original string.
The second argument will be your regex pattern you want to put a a character after. In this case it is . (any character) occurring 2 times. It is surrounded by parentheses which will be needed for the next argument to specify a capture group.
The third argument is using \1 to specify the first capture group, then you can put anything you'd like to appear after the capture group. In the example below I used a !.
SELECT REGEXP_REPLACE ('12345678', '(.{2})', '\1!') as str FROM DUAL;
STR
_______________
12!34!56!78!
If you do not want the character at the end of your string, you can TRIM it from the right side or SUBSTR if the special character may appear at the end of the original string.

Answer 2

You can use an hierarchical query during the split and padding a special character through use of DBMS_RANDOM.VALUE in order to produce some special characters except for the last piece, and then LISTAGG() function to combine the pieces back again such as
SELECT id,LISTAGG( SUBSTR(col,1+(level-1)*2,2)||
CASE WHEN level < CEIL(LENGTH(col)/2)
THEN
CHR(TRUNC(DBMS_RANDOM.VALUE(33,48)))
END)
WITHIN GROUP (ORDER BY level)
AS result
FROM t
GROUP BY id
CONNECT BY level <= CEIL(LENGTH(col)/2)
AND PRIOR SYS_GUID() IS NOT NULL
AND PRIOR ID = ID
Demo