User's Guide and Reference

Data types for multi-unit features

Use ST_MultiPoint, ST_MultiLineString, and ST_MultiPolygon to store coordinates that define spaces occupied by features that are made up of multiple units:

• Use ST_MultiPoint when you want to represent features made up of discrete units, and you want to indicate the point in space occupied by each component. An ST_MultiPoint data item includes the pairs of X and Y coordinates that define the location of each component of such a feature. For example, consider a table whose rows represent island chains and whose columns include an ST_MultiPoint column. Each data item in this column includes the pairs of X and Y coordinates that define the locations of the islands in each chain.
• Use ST_MultiLineString when you want to represent features made up of linear units, and you want information about the space occupied by each unit. An ST_MultiLineString data item consists of the coordinates that define such spaces. For example, consider a table whose rows represent river systems and whose columns include an ST_MultiLineString column. Each data item in this column includes the sets of coordinates that define the paths of the rivers in each system.
• Use ST_MultiPolygon when you want to represent features made up of multi-sided units, and you want information about the space occupied by each unit. For example, consider a table whose rows represent midwestern counties and whose columns include an ST_MultiPolygon column. This column contains information about farmlands. Specifically, each data item in the column includes the sets of coordinates that define the perimeters of the farmlands in a particular county.