id,page,ref,title,content,breadcrumbs,references
spatialite:installing-spatialite-on-linux,spatialite,installing-spatialite-on-linux,Installing SpatiaLite on Linux,"SpatiaLite is packaged for most Linux distributions. 
                 apt install spatialite-bin libsqlite3-mod-spatialite 
                 Depending on your distribution, you should be able to run Datasette something like this: 
                 datasette --load-extension=/usr/lib/x86_64-linux-gnu/mod_spatialite.so 
                 If you are unsure of the location of the module, try running  locate mod_spatialite  and see what comes back.","[""SpatiaLite"", ""Installation""]",[]
spatialite:querying-polygons-using-within,spatialite,querying-polygons-using-within,Querying polygons using within(),"The  within()  SQL function can be used to check if a point is within a geometry: 
             select
    name
from
    places
where
   within(GeomFromText('POINT(-3.1724366 51.4704448)'), places.geom); 
             The  GeomFromText()  function takes a string of well-known text. Note that the order used here is  longitude  then   latitude . 
             To run that same  within()  query in a way that benefits from the spatial index, use the following: 
             select
    name
from
    places
where
    within(GeomFromText('POINT(-3.1724366 51.4704448)'), places.geom)
    and rowid in (
        SELECT pkid FROM idx_places_geom
        where xmin < -3.1724366
        and xmax > -3.1724366
        and ymin < 51.4704448
        and ymax > 51.4704448
    );","[""SpatiaLite""]",[]
spatialite:spatial-indexing-latitude-longitude-columns,spatialite,spatial-indexing-latitude-longitude-columns,Spatial indexing latitude/longitude columns,"Here's a recipe for taking a table with existing latitude and longitude columns, adding a SpatiaLite POINT geometry column to that table, populating the new column and then populating a spatial index: 
             import sqlite3

conn = sqlite3.connect(""museums.db"")
# Lead the spatialite extension:
conn.enable_load_extension(True)
conn.load_extension(""/usr/local/lib/mod_spatialite.dylib"")
# Initialize spatial metadata for this database:
conn.execute(""select InitSpatialMetadata(1)"")
# Add a geometry column called point_geom to our museums table:
conn.execute(
    ""SELECT AddGeometryColumn('museums', 'point_geom', 4326, 'POINT', 2);""
)
# Now update that geometry column with the lat/lon points
conn.execute(
    """"""
    UPDATE museums SET
    point_geom = GeomFromText('POINT('||""longitude""||' '||""latitude""||')',4326);
""""""
)
# Now add a spatial index to that column
conn.execute(
    'select CreateSpatialIndex(""museums"", ""point_geom"");'
)
# If you don't commit your changes will not be persisted:
conn.commit()
conn.close()","[""SpatiaLite""]",[]
spatialite:spatialite-installation,spatialite,spatialite-installation,Installation,,"[""SpatiaLite""]",[]