Explanation:
: INSTR is a character function return the numeric position of a named string.
INSTR(NAMED,’a’) Incorrect answer :
2: Did not return a numeric position for ‘a’.
3: Did not return a numeric position for ‘a’.
4: Did not return a numeric position for ‘a’.
Reference:
Introduction to Oracle9i : SQL, Oracle University Study Guide, 3-8

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