El Tquery permite ser filtrado con las propiedas filter y filtered. La primera indica la condición del filtro, y la segunda establece si se aplica o no, "true" o "false". Para que el filtro tenga efecto filtered debe ser "true".
La ayuda de Delphi sobre la propiedad filter ayuda bastante:
property Filter: String;
Description
Use Filter to specify a dataset filter. When filtering is applied to a dataset, only those records that meet a filter’s conditions are available to an application. Filter contains the string that describes the filter condition. For example, the following filter condition displays only those records where the State field is 'CA' or 'MA':
State = 'CA' or State = 'MA'
To filter strings bases on partial comparisons, use an asterisk as a wildcard. For example:
State = 'M*'
Note: Applications can set Filter at runtime to change the filtering condition for a dataset at (for example, in response to user input).
