[GRASS-dev] Re: [GRASS-user] v.db.join script

[Micha Silver]

Moritz Lennert wrote:

> On 13/10/10 22:23, Micha Silver wrote:
>> One line from the v.db.join script uses grep and cut to get the column
>> names and the next line gets the column types like so:
>>
>> db.describe -c bike_rides2 | grep '^Column' | cut -d ':' -f 3
>> INTEGER
>> CHARACTER
>> INTEGER
>> CHARACTER
>> CHARACTER
>> CHARACTER
>> CHARACTER
>>
>> So the column size is actually ignored.
>>
>> Next, in the script the above output is used by v.db.addcol to create
>> the new columns in the joined vector. So all new character columns are
>> created as a single char and the actual length is never used.
>>
>> Questions:
>> Is the db.describe output the same for all db drivers?
>> Any suggestions how to fix this as a script?
>
> Why not use an SQL join, i.e. something like the following ?
>
> 1) CREATE TABLE temp AS (SELECT * FROM $maptable JOIN $otable ON 
> $column=$ocolumn)
>
> 2) rename table $maptable to something else
>
> 3) rename table temp to $maptable
>
> 4) if this works, remove the original $maptable
>
Interesting. So your suggestion is to run the above sql commands thru 
db.execute to create a new attribute table for an existing vector?

> Not tested, but might be a more elegant solution ?
>
> Moritz
>
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