Re: Copy and concatenate a vector attribute between layers
Peter Tittmann <[email protected]>
| Newsgroups | gmane.comp.gis.grass.user |
|---|---|
| Message-ID | <[email protected]> |
Thank you, Moritz. I'm pretty familiar with SQL but can’t figure out how layer 2 is stored in the database. When I `pragma table_info(<vector>)` I only see the layer 1 attributes. I’ll work with the GRASS approach you suggested. Best, Peter > On Dec 1, 2017, at 11:53 PM, Moritz Lennert <[email protected]> wrote: > > On 02/12/17 02:03, Peter Tittmann wrote: >> Hi, >> I have a vector (`POINT`) which has two layers containing relevant attributes (’strata’ and ’stand’). I would like to concatenate the two values into a new attribute for Layer 1 (’<STRATA>_<STAND>’). I’ve been struggling to sort this out for too long and am tapping out. Its probably blatantly obvious but it has escaped me. > > > Probably the easiest way if your not very familiar with SQL: > > - Create a new column in layer 1 where you can put the info from layer 2 > - Fill this column with v.to.db option=query query_layer=2, etc > - Create a second new column to hold the concatenation > - v.db.update to update this new column with the concatenation of the two others (something like qcol = "STRATA || '_' || STAND") > > Otherwise, if there is a common key in both tables, you can just create a new column and use db.execute to launch a UPDATE TABLE directly, grabbing the info from the two table and concatenating it directly in the query. > > Moritz > > >> Thank you! >> Here are some specifics. >> east, north: 651849.842735, 6604949.78485 >> c34_patch@project_area: >> Type: Point >> Id: 21622 >> Layer: 1 >> Category: 21623 >> Driver: sqlite >> Database: /Users/pete/grassdata/PortGraham/project_area/sqlite/sqlite.db >> Table: c34_patch >> Key_column: cat >> Attributes: >> cat: 21623 >> *strata: 3 — STRATA* >> c34_patch@project_area: >> Type: Point >> Id: 21622 >> Layer: 2 >> *Category: 10 — STAND* >> _______________________________________________ >> grass-user mailing list >> [email protected] <mailto:[email protected]> >> https://lists.osgeo.org/mailman/listinfo/grass-user <https://lists.osgeo.org/mailman/listinfo/grass-user> _______________________________________________ grass-user mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/grass-user