I have a spatialite table with more than 1100 Polygons. The geometry type in that table is multipolygon. There are only some real Multipolygons inside and I need only polygons. How can I find the multiparts? How can I split the multiparts? Also are there some polygons without geometry. What is the way to identify them? I want to do that work in the database but could do it also in QGIS.
In SpatiaLite, you can use the function ElementaryGeometries such as the following code :
SELECT ElementaryGeometries('multipoly', 'geom', 'singlepoly','gid','fid') as geom FROM multipoly
This function create a new table singlepoly where each multipolygon of the table multipoly is converted to a simple polygon. For example, I had one feature. For example, I had a multi-polygon with 4 features. On output, I get a table with 4 rows.
In QGIS, you can use the following tool :
Vector > Geometry tools > Multipart to Singleparts.