How to find a substring in a given string using the INSTR() function?

INSTR(str, substr) is a MySQL built-in function that locates a substring in a string and replace it with a new string. For example:

SET @str = 'dba.FYIcenter.com';

SELECT INSTR(@str, 'FYI');
  -- +--------------------+
  -- | INSTR(@str, 'FYI') |
  -- +--------------------+
  -- |                  5 |
  -- +--------------------+

Reference information of the INSTR() function:

INSTR(str, substr): pos
  Returns the position of the first occurrence of substring substr in
  string str. This is the same as the two-argument form of LOCATE(),
  except that the order of the arguments is reversed.

Arguments, return value and availability:
  str: Required. The string that will be searched in.
  substr: Required. The substring to search for.
  pos: Return value. The position where is substring is located.
  Available since MySQL 4.0.

Related MySQL functions:

• LOCATE() - Locate Substring Starting at N
• POSITION() - Synonym for LOCATE()

⇒ LCASE() - Synonym for LOWER()

⇐ INSERT() - Insert and Replace Substring

⇑ MySQL Functions on Character String Values

⇑⇑ MySQL Function References