attribute-joinscsvexportqgis
I am joining a .csv file with a shapefile in QGIS 2.18.12 and I need the column names for further processing (but they are way longer than 10 digits). However, when I save the new file, the column names are changed by GQIS. I found a manual way here. But my .csv file has 253 columns, therefore a manual processing afterwards is not reasonable.
Is there any way to export my file with the column names of the csv file, or change the column names of the shapefile afterwards in an automated way?
Relates work with a 1:M relationship between two tables. Right-click the layer to define the Relate. After defining the Relate, the Identify Tool will list the related records also.
It's best if you make sure the two fields have the same data type.
The field type can't be changed for shapefiles. But it's easy to create a new empty text field and make that equal to the integer field.
You can use a field calculator expression that looks something like:
tostring( "INT_FIELD" ) and simply replace INT_FIELD with the name of the actual integer field.
You can easily change a CSV layer attribute value from text <-> number too.
If you are getting null values, you could try keeping the join, but just close and re-open that attribute table to see if the joined values are there (or even close/re-open QGIS).
I've been able to successfully join a csv to a shapefile with a mixture of field types so string vs integer shouldn't be the issue.
Looks like in order to get rid of the null values, they have to actually have a matching record in the corresponding table that joins are being made from. But in the image below, you can see that some do have a matching record:
Best Answer
The 10-character limit for column names is a limitation of the shapefile format. So the easiest solution is to use format that allows longer column names, such as geopackage.
If for some reason you must use shapefiles, give each column a short name before importing into QGIS. In Excel, it would be very simple to add a row, fill the first value as "field1", then click and drag across the row to auto-fill with field2, field3, etc.
Now the first two rows of your spreadsheet are:
Save these two rows as a separate spreadsheet.
Delete the second row from the CSV before importing into QGIS.
You won't be able to import the original column names into a shapefile, because the 10-character field name limit still applies. But after any processing you do in QGIS, you can export the layer as a CSV and add the original column names. Open the exported CSV in Excel, make sure the columns are in numerical order, and insert the row of original column names.