MySQL ELT() function returns NULL as output if the index number provided as argument is higher than the number of strings. Following is an example to make it clearer −
Example
mysql> Select ELT(6,'Ram','is','a','good','boy')As Result; +--------+ | Result | +--------+ | NULL | +--------+ 1 row in set (0.00 sec)
As we can see that index number is 6 and the list of strings is having only 5 strings. Hence MySQL returns NULL.