I would like to get only one feature from a MySQL database.
I use the Add Vector Layer functionality in QGIS to get the features (polygons) from the MySQL database. They are all displaying fine, but my problem is that I would like to get only one feature/polygon from the database, filtering by a MySQL query by example (it would be perfect).
Is there a way to do so ?
When you connect to your database and after you selected the table your wish to view, there is a button which says "Build Query". And then you tell qgis which features you want to fetch.
If for some reason you cannot access the build-in query builder you can create a View.
Go in the database and enter,
CREATE OR REPLACE VIEW myView AS SELECT * FROM <SPATIAL_TABLE> where <constraints>;
And then point QGIS at the created view. Also check How to create a table from existing tables (applying new schemas) in postgis DB? for more details.
I found a solution using the ogr2ogr executable, which supports MySQL (if you're using PostgreSQL, see pgsql2shp and shp2pgsql). I'm using it like this and it works fine.
ogr2ogr -overwrite -where "YOUR SQL CONDITION" -f "ESRI Shapefile" SHPCREATED.shp MYSQL:vine,host=localhost,user=root YOURTABLE
If you're under Mac OS X, the executable has been installed in /Library/Frameworks/GDAL.framework/Versions/1.9/Programs/
I was looking for a solution which was possible in command-line, because I'm working on a website and I would like to do these tasks automatically. Therefore, this is perfect for me.