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# zones table structure

The zones table holds information on the Traffic Analysis Zones (TAZs) in AequilibraE’s model.

The zone_id field identifies the zone.

The area field corresponds to the area of the zone in km2. TAZs’ area is automatically updated by triggers.

The name fields allows one to identity the zone using a name or any other description.

Field | Type | NULL allowed | Default Value
--- | --- | --- | ---
ogc_fid* | INTEGER | YES |
zone_id | INTEGER | NO |
area | NUMERIC | YES |
name | TEXT | YES |
geometry | MULTIPOLYGON | NO | ‘’

(* - Primary key)

The SQL statement for table and index creation is below.

    CREATE TABLE 'zones' (ogc_fid    INTEGER PRIMARY KEY,
                          zone_id    INTEGER UNIQUE NOT NULL,
                          area       NUMERIC,
                          "name"     TEXT);

    SELECT AddGeometryColumn( 'zones', 'geometry', 4326, 'MULTIPOLYGON', 'XY', 1);
    CREATE UNIQUE INDEX idx_zone ON zones (zone_id);
    SELECT CreateSpatialIndex( 'zones' , 'geometry' );
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('zones','zone_id', 'Unique node ID');
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('zones','area', 'Area of the zone in km2');
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('zones','name', 'Name of the zone, if any');