Multi-level directories. To create this kind of reference will require a slightly different database structure. Indeed, as already mentioned, these guides created to facilitate the selection of values from the list with a large number of records that are filtered by the selected value (parameter) in another list. This means that it will take to link the two reference tables, organizing one component directory. The previous chapter proposed instead of creating a set of similar guides do a mock search form and cling to him a source of data at startup.
But you can delve even further. We use the idea which suggested Valeriy Kruk – do one lookup table and will store its data to all the directories. This will require another field – the identifier "information table" to determine which directory is the record. And for the realization of two-level directory will create a second table in which to store related to the first table entry. Table Name Field Name Field Type directory id counter Text Name Type Long Integer directory Sub id counter id1 Long Integer Name Text When you install the relationships between tables directory and directory Sub to select "Cascade Delete Related Records" – this is the case when such a procedure would be useful. After all, when you delete records from a table "DIRECTORY" related data is not necessary. If you open a data schema, you'll see only two related reference tables. In the previous example to the main table, "addressee" had tied all directories, and I have talked in detail about the links, check boxes