Tables are the basic objects in the database used to store data as well as data about data (metadata). In a geodatabase, there are system tables that store information about the other tables, records, and indexes in the geodatabase. These are called metadata tables or repository tables.
There are also classes of tables in the geodatabase that work collectively to store specific types of spatial data. For example, feature classes store information about spatial features. They are made up of several tables, depending on the DBMS you use to store them and whether they are versioned. These spatial data tables have the same properties as nonspatial tables plus they have spatial properties.
General table properties
- Tables manage attributes. This means they store information. In a geodatabase, tables usually store information about a geographic entity.
- Tables contain rows. Each row is one record. In a spatial table, each row represents one feature.
- All rows in a table have the same columns. Columns are also called fields. They are the categories of information the table contains, such as names, areas, statuses, or ID numbers.
- Each field has a data type and a name.
Spatial table properties
(These properties are in addition to the general table properties.)
- Spatial tables have x,y coordinates.
- Spatial tables can have measure(m-) and z-coordinates.
- Spatial tables have a spatial reference. This includes a coordinate system, x,y tolerance, z- and/or m-tolerance (if z- and/or m-coordinates are present), and resolution.
- Spatial tables store a specific type of feature—polygon, line, point, multipoint, multipatch, dimension, or annotation.
You can define table names, field names, and data types when you use ArcGIS to create tables in a geodatabase. For spatial tables such as feature classes, you also define whether m- and z-coordinates will be present, the coordinate system, the tolerance values, and what type of data will be stored.
You can use context menus in the Catalog pane or geoprocessing tools to create new tables or feature classes. If using geoprocessing tools, you don't create new fields; you can import empty fields from an existing table, but new fields must be defined after the table or feature class is created.