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I have a shapefile with several attributes, for example YEAR, COUNTY, and AREA. I also have a CSV file with more fields that I want in the shapefile, such as POPULATION. Both the shapefile and the CSV file have a field GISJOIN. I know how to do a join in QGIS. But how can I make a permanent join and write to a shapefile using ogr2ogr or one of the other tools in GDAL/OGR?

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Does your GDAL/OGR build have spatialite or sqlite support? –  BradHards May 13 '14 at 0:30
    
@BradHards: It doesn't look like it. It's the packaged GDAL/OGR build from Ubuntu 14.04. –  Lincoln Mullen May 13 '14 at 0:48

2 Answers 2

up vote 10 down vote accepted

The ogr2ogr utility supports a limited sql syntax. You can join your CSV to the shapefile using something like the following:

ogr2ogr -sql "select inshape.*, joincsv.* from inshape left join 'joincsv.csv'.joincsv on inshape.GISJOIN = joincsv.GISJOIN" shape_join.shp inshape.shp
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Oh gdal/ogr - you never cease to amaze me.. –  radek May 13 '14 at 7:49

The accepted answer is really useful, but I found that it was slow with a large-ish database. I believe it also limits your options when joining the data.

My method now is to pull everything into SQLite (using a combination of csvkit and ogr2ogr):

csvsql --db sqlite:///myjoindb.db --insert myjoincsv.csv
ogr2ogr -append -f "SQLite" myjoindb.db myjoinshp.shp

Then join everything and create a shapefile out of it:

ogr2ogr -f "ESRI Shapefile" -sql "SELECT csv.*, shp.* FROM myjoinshp shp INNER JOIN myjoincsv csv ON csv.joinfield = shp.joinfield" joined_output.shp myjoindb.db
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Hey Eric, I'm getting an error that myjoindb.db already exists. Is that secondline db supposed to be named same as first? –  GIS Danny Apr 17 at 21:46
    
Ah good point, on the second line you'll want to add a -append in there to give ogr2ogr permission to open up an existing SQLite db and add to it. I've edited the answer to show this. –  eric brelsford Apr 19 at 20:07
    
Thanks! Working great. One more question, hopefully quick. The first line, I have a field geoid that keeps getting weirdly converted to negative floats. It's a census id that I want to treat as string, I've tried wrapping the string with quotes and that didn't work. Is there a command like: csvsql --db sqlite:///myjoindb.db --insert myjoincsv.csv geoid.map(str) or something? –  GIS Danny Apr 23 at 16:27
    
What's weird is the join occurs correctly on geoid but the output has the geoid with -2147184982 instead of what went into it. –  GIS Danny Apr 23 at 16:41
    
Sounds like geoid is being converted to a number, but the number is so large that it overflows and becomes negative. Check the documentation for csvsql, you might try specifying a table where you explicitly say that geoid is a string, else --no-inference might help. –  eric brelsford Apr 23 at 20:30

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