id

Unique number assigned by the database to identify a record

A number that is a meaningful reference for the database but not of much use to a human user. Use in displayed fields when counting records or in filters.

text

Text field

Usually uses the Raw Data transform.

timestamp

Exact date and time

Select appropriate date/time transform. Raw Data includes second and timezone information, usually more than is required for a report.

bool

True or False

Commonly used to filter out deleted item or patron records.

org_unit

A number representing a library, library system, or federation

When you want to filter on a library, make sure that the field name is on an org_unit or id data type.

link

A link to another database table

Link outputs a number that is a meaningful reference for the database but not of much use to a human user. You will usually want to drill further down the tree in the Sources pane and select fields from the linked table. However, in some instances you might want to use a link field. For example, to count the number of patrons who borrowed items you could do a count on the Patron link data.