To use SQL Statements with variable values, e.g. from SFormattedFields in Forms or PFormattedFilds in Reports, there are placeholder constructs, to execute the statement with the corresponding values.
So
can be used, wich will be replaced by the corresponding values when executiong the SQL Statement.
The vorehold part of these constructs describes the kind of the data, therefor from a Form, a Report or a Systemvariable. The second part separated by the exclamation mark defines the unique name of the source, e.g. the SFormattedField in forms.