Equality

= 

Returns entries containing attribute values that exactly match the specified value. For example, cn=Bob Johnson

Substring

=string*string

Returns entries containing attributes containing the specified substring. For example, 

cn=Bob*cn=*Johnsoncn=*John*cn=B*John

(The asterisk (*) indicates zero (0) or more characters.) 

Greater than or equal to

\>= 

Returns entries containing attributes that are greater than or equal to the specified value. For example, 

buildingname \>= alpha

Less than or equal to

<= 

Returns entries containing attributes that are less than or equal to the specified value. For example, 

buildingname <= alpha

Presence

=* 

Returns entries containing one or more values for the specified attribute. For example, 

cn=*

telephonenumber=*

manager=*

Approximate

~= 

Returns entries containing the specified attribute with a value that is approximately equal to the value specified in the search filter. For example, 

cn~=suret

l~=san fransico

could return 

cn=sarette

l=san francisco

The Approximate operator is experimental and works only with English language strings. It does not work with non-ASCII based strings, such as Ja or Zn.