Question

I have a column with values as below:

BOOK # ,7,8
BOOK # ,2
BOOK # ,13,14

I am generating above column with complex xml aggregate function as below:

SELECT 
CONCAT('BOOK # ',XMLSERIALIZE(XMLAGG(XMLTEXT(CONCAT(',', SUBSTR(TRIM(TEMP.BOOK_NUM),    
LOCATE('.',TEMP.BOOK_NUM)+1)))) AS VARCHAR(1024 )))
FROM TEMP 
GROUP BY BOOK_ID

Temp.book_num is of type 123.2, 123.4 in two different rows. So book_id 123 will have two books 2, 4. Thus to extract 2 and 4 out of two rows of same book_id, I had to write above query.

As clear there is an extra ‘,’ comma coming after the words ‘BOOK #’ which is redundant and unrequired.

I am not able to modify above query to remove it.

Is there any way possible to remove the first occurrence of a character (comma here) from a column value which could be accomodated in the query above ?

My output should be:

BOOK # 7,8
BOOK # 2
BOOK # 13,14

Thanks for reading!

Answer 1

Although the wording is almost identical, it’s a lot easier to remove the first character than it is to remove the first occurrence of a specific character. Fortunately, just removing the first character will solve your problem. You can do that by stuffing your XMLSERIALIZE() expression into a SUBSTR() call like this:

CONCAT('BOOK # ',
    SUBSTR(
        XMLSERIALIZE(XMLAGG(XMLTEXT(CONCAT(',', SUBSTR(TRIM(TEMP.BOOK_NUM),  
           LOCATE('.',TEMP.BOOK_NUM)+1)))) AS VARCHAR(1024))
       ,2
    )
)

Thanks to Serge Rielau for posting this trick in his blog.