CCK Field Table in Database and Content Type
Assuming you're using CCK with Drupal 6 here...

Unless a field is set to multiple cardinality, or is attached to more than one content type, there won't be a table created for it. Instead, a new column will be created for it in the CCK table for that content type.

For example, if you have a content type called 'page' with a number field called 'field_number', with single cardinality and only attached to the 'page' type, there will be a column called field_number_value in the content_type_page table; that's where the data is stored.