Select the expression that causes a MySQL error.

Hint:

the RAND$()$ function in SQL typically generates a single random value, not a random value for each row in a result set.

GROUP$\_$CONCAT$($amount ORDER BY RAND$())$ concatenates all the amount values for each customer$\_$id$,$ with the ORDER BY RAND$()$ clause ensuring that the values are concatenated in a random order.

SUBSTRING$\_$INDEX$()$ extracts the first value from the concatenated string, which effectively gives you a random amount for each customer$\_$id$.$

Question $2$ options:

SELECT customer$\_$id$,$ ANY$\_$VALUE $($amount$)$ FROM transactions GROUP BY customer$\_$id

SELECT customer$\_$id$,$ RAND $($amount$)$ FROM transactions GROUP BY customer$\_$id

SELECT customer$\_$id$,$ SUBSTRING$\_$INDEX$($GROUP$\_$CONCAT $($amount ORDER BY RAND$()),\text{'},\text{'},1$ FROM transactions GROUP BY customer$\_$id

none of the above