ogr2ogr dissolve shapefile

Question

I am following this question with the first answer Dissolve/aggregate polygons with ogr2ogr or gpc? where I am trying to dissolve my shapefile down to 1 row by the geometry field

ogr2ogr C:\Users\name\Desktop\output.shp C:\Users\name\Desktop\All_constraints_v5.shp -dialect sqlite -sql "SELECT ST_Union(geometry) FROM input"

ERROR 1: In ExecuteSQL(): sqlite3_prepare(SELECT ST_Union(geometry) FROM input):
 no such table: input

right so then I did

C:\Program Files\GDAL>ogrinfo -so C:\Users\rizagha\Desktop\All_constraints_v5.shp
INFO: Open of `C:\Users\rizagha\Desktop\All_constraints_v5.shp'
      using driver `ESRI Shapefile' successful.
1: All_constraints_v5 (Polygon)

So my question is

"SELECT ST_Union(geometry) FROM input" does input need to be my shp full path variable? what is the exact syntax
I cannot find out what the geometry column is called.

I ran this:

C:\Program Files\GDAL>ogrinfo -geomfield -fields=YES C:\Users\rizagha\Desktop\All_constraints_v5.shp
INFO: Open of `C:\Users\rizagha\Desktop\All_constraints_v5.shp'
      using driver `ESRI Shapefile' successful.
1: All_constraints_v5 (Polygon)

but it doesn't tell me what column name the geom is

As ogrinfo shows, your layer name is All_constraints_v5 and that is what you will use for FROM. Geometry field is "geometry" for the SQLite dialect. — user30184, Dec 20 '17 at 16:03
@user30184 put it as answer so I can close this question out — ziggy, Jan 02 '18 at 14:06

score 4 · Accepted Answer · answered Jan 02 '18 at 21:55

4

As ogrinfo shows, the layer name is All_constraints_v5 and therefore the righ command is

ogr2ogr C:\Users\name\Desktop\output.shp C:\Users\name\Desktop\All_constraints_v5.shp -dialect sqlite -sql "SELECT ST_Union(geometry) FROM All_constraints_v5"

answered Jan 02 '18 at 21:55

user30184

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ogr2ogr dissolve shapefile

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