* - If the value is an array, an IN(...) clause will be constructed,
* such that the field name may match any of the elements in the
* array. The elements of the array will be quoted.
- * - If the field name ends with "!", this is taken as a flag which
- * inverts the comparison, allowing NOT IN clauses to be constructed,
- * for example: array( 'user_id!' => array( 1, 2, 3 ) )
*
* Note that expressions are often DBMS-dependent in their syntax.
* DBMS-independent wrappers are provided for constructing several types of