CHOOSE - Choose a string from a list of strings in Informatica

CHOOSE function is used to pick a string from a set of strings by giving its position number. Position number starts at 1 and infa returns NULL if a string is not found at a specified position.
CHOOSE( index, string1 [, string2, ..., stringN] )

Example : Pick the second string
CHOOSE( 2, 'Apple', 'Orange', 'Mango' )

Output : Orange
Example : String not found
CHOOSE( 4, 'Apple', 'Orange', 'Mango' )

output : NULL