How to find a string in a given string list using the FIELD() function?

FIELD(str, str1, str2, ...) is a MySQL built-in function that searches for a string in a given string list. For example:

SET @obj = 'Apple';

SELECT FIELD(@obj, 'Orange', 'Banana', 'Apple');
  -- +------------------------------------------+
  -- | FIELD(@obj, 'Orange', 'Banana', 'Apple') |
  -- +------------------------------------------+
  -- |                                        3 |
  -- +------------------------------------------+

Reference information of the FIELD() function:

FIELD(str, str1, str2, ...): idx
  Returns the index (position) of str in the str1, str2, str3, ... list.
  Returns 0 if str is not found.

  If all arguments to FIELD() are strings, all arguments are compared as
  strings. If all arguments are numbers, they are compared as numbers.
  Otherwise, the arguments are compared as double.

  If str is NULL, the return value is 0 because NULL fails equality
  comparison with any value.

Arguments, return value and availability:
  str: Required. The string to search for in the string list.
  str1, str2, ...: One or more strings to form the string list.
  idx: Return value. The index of the string list where the given is found.
  Available since MySQL 4.0.

Related MySQL functions:

• ELT() - String at Given Index

⇒ FIND_IN_SET() - Find Substring in List String

⇐ ELT() - String at Given Index

⇑ MySQL Functions on Character String Values

⇑⇑ MySQL Function References