Compatibility
INSTR(s1, s2)
Engine	OK	Alternative
ingres	No	POSITION(s2 IN s1)
mysql	Yes
oracle	Yes
postgres	No	POSITION(s2 IN s1)
sqlserver	No	PATINDEX('%'+s2+'%',s1)

INSTR

INSTR(s1, s2) returns the character position of the substring s2 within the larger string s1. The first character is in position 1. If s2 does not occur in s1 it returns 0.

    INSTR('Hello world', 'll') -> 3

In this example you get the position of string 'an' within a country's name.

SELECT name,
       POSITION('an' IN name)
  FROM bbc

SELECT name,
       PATINDEX('%an%', name)
  FROM bbc
 ORDER BY name

SELECT name,
       INSTR(name, 'an')
  FROM bbc