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I am quite new to postgres/postgis and are still learning basic skills. I have imported a pointlayer shapefile into my postgres database.

I need to make a buffer of varying radius around the points depending on attribute. I have been reading about the ST_buffer function in the documentation but I am having problems to interpreting it so far.

I am trying to use SELECT geometry ST_Buffer(geometry g1, float radius_of_buffer);

I have tried SELECT geometry ST(mypoints.geom, 100) FROM myschema.mypoints

I hope someone could help me to write it out properly

Best Regards

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    SELECT ST_Buffer(geom, 100) FROM myschema.mypoints
    – John Powell
    Commented Feb 11, 2015 at 9:02

1 Answer 1

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If you want a conditional buffering based on some attribute, you can use a case statement, eg,

SELECT ST_Buffer(geom, CASE WHEN atr = 0 then 10 WHEN atr=1 THEN 20 ELSE 30 END) 
FROM mypoints;

Obviously, you can have as many WHENs as you like, though it could get cumbersome fast. If it is a straight multiplier, then you can just do ST_Buffer(geom, atr * 2), for example.

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  • Thank you! <br/> I think I will use views and create one view for each attribute that need another buffer size. I have about 10 different attributes that need their own buffer size.
    – geogrow
    Commented Feb 11, 2015 at 9:15
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    Great. If it has helped, please accept. I have edited your question to, I hope, better reflect what you are asking. Please re-edit if you disagree with me.
    – John Powell
    Commented Feb 11, 2015 at 9:18
  • Can you use conditional buffering based on attribute from a different table? <br/>
    – geogrow
    Commented Feb 19, 2015 at 14:04
  • Yes, assuming you can join it somehow to the first table?
    – John Powell
    Commented Feb 19, 2015 at 14:06
  • Wow, that was a super fast reply! I went to edit my question bc I accidentally posted it before it was done =) I have created a view in my postgres db. I want the user to be able to put in any value in a column that the buffer radius will be generated from. In that way will the buffer be generated on the fly
    – geogrow
    Commented Feb 19, 2015 at 14:09

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