[GRASSLIST:9806] Re: Solved: way to drop column in sqlite3

[Stephan Holl]

Hello Wolfgang, 

On Thu, 12 Jan 2006 14:00:36 +0100 wqual <wolfgang.qual at gmx.net> wrote:

> Hi list,
> I just found out that there is a way to drop columns in sqlite. It is
> not this alter table drop column command, but another one [1]
> 
> "BEGIN TRANSACTION;
> CREATE TEMPORARY TABLE t1_backup(a,b);
> INSERT INTO t1_backup SELECT a,b FROM t1;
> DROP TABLE t1;
> CREATE TABLE t1(a,b);
> INSERT INTO t1 SELECT a,b FROM t1_backup;
> DROP TABLE t1_backup;
> COMMIT;"
> 
> It's obvious that this is a little bit complex. But if you use
> sqlitebrowser, you will find under -->modify table  a button "remove
> field".
> 
> Best regards,
> 
> Wolfgang
> 
> 
> [1] http://www.sqlite.org/faq.html#q13

Nice one. I think this should find the way into the GRASS-wiki on [1].

What do you think?

Best 
	Stephan

[1] http://grass.gdf-hannover.de/

> 
> ----------------------
> 
> Am Dienstag 10 Januar 2006 pH:20:16 nachmittags/abends schrieb
> Wolfgang Qual:
> > Hi everybody,
> > I just read that SQLITE also does not support "ALTER TABLE table
> > DROP COLUMN". ("SQLite's version of the ALTER TABLE command allows
> > the user to rename or add a new column to an existing table. It is
> > not possible to remove a column from a table." [1]
> > How to deal with this issue?
> >
> > Best regards,
> > Wolfgang
> >
> > [1] http://www.sqlite.org/lang_altertable.html
> >
> > -----
> >
> > > --- Ursprüngliche Nachricht ---
> > > Von: M S <mseibel at gmail.com>
> > > An: Markus Neteler <neteler at itc.it>
> > > Kopie: GRASS Users List <grasslist at baylor.edu>
> > > Betreff: [GRASSLIST:9717] Re: drop column?
> > > Datum: Wed, 4 Jan 2006 12:06:46 -0500
> > >
> > > yes sorry, that was for the DBF driver.  shoot, thats too bad.  i
> > > guess i'd have to (from reading the archives) create a temp table
> > > and copy over only the colums I want and then re-attach it?  that
> > > might be a handy function.
> > >
> > > anyhow, learning postgres is on my TODO list, so hopefully this
> > > issue goes away with more knowledge.
> > >
> > > thanks!
> > >
> > > On 1/4/06, Markus Neteler <neteler at itc.it> wrote:
> > > > M S wrote:
> > > > >is there a drop column command? i didnt see one in the man
> > > > >pages, and when i tried the    "ALTER TABLE table DROP COLUMN
> > > > >column_name" | db.execute   it didnt like that command but i
> > > > >was able to add columns..
> > > >
> > > > It depends on the DB driver. I assume that you use DBF? Then it
> > > > doesn't work since DBF is very limited. For all other drivers
> > > > it should
> > >
> > > (untested).
> > >
> > > > Markus


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