This chapter refers to both columns and fields. Conventionally, database tables are composed of columns, and the columns divide each row or record into fields. Some Domain operations refer to columns, others to fields, but these terms refer to the same concept from different perspectives. For example, a calculated field refers to a field that is computed from the other field values in the same row or record. But the effect of a calculated field in every row is to create a new calculated column. Similarly, operations such as joins and filters operate on designated field values in a row, but they are defined by the columns that determine the fields involved.
Within a Domain, columns are called items. Because an item may originate from derived tables or calculated fields, it may not correspond to a single column in the database.
Measures are columns or fields that display numeric values or aggregate values in reports. Measures are the quantitative values of a record, such as an amount, as opposed to qualitative values such as name or location. Having a field designated as a measure determines where the item can be placed in the report. For example, measures appear summarized in the center of crosstabs, whereas only non-measures, simply called fields, can be used as row and column groups of the crosstab. In Domains, all items based on numeric fields are designated as measures by default, but you can set them manually as well. By marking items as measures, Domains help report creators find and use the data they need in the Ad Hoc Editor.