Re: [GRASS-user] POW() in SQLite?

2010-03-02 Thread Hamish 
 Hamish wrote:
  I am trying to use POW(x,n) with SQLite but it fails:
...
  no such function: POW

Glynn:
 Nope; not in SQLite:
 http://www.sqlite.org/lang_corefunc.html
 
..
  Similar problem if I try x^n:
  unrecognized token: ^
 
 SQLite doesn't have a power operator:
 http://www.sqlite.org/lang_expr.html#binaryops


 
  this random webhit suggests that it should be possible:
http://osdir.com/ml/sqlite-users/2009-03/msg00248.html
 
 That says:
..
 Note: in addition to the SQLite default. IOW, those
 functions are added by SQLiteSpy, and are not part of SQLite.

ah, skimming error.


Rich:
 I'd manipulate those values first, then pass them to SQLite.


solution:

#no good:
#v.db.update basemap column=volume value=POW(length,3) --verbose

#good:
v.db.select basemap column=cat,length | awk -F'|' \
  '{printf(UPDATE basemap SET volume=%f WHERE cat=%d;\n, $2^3, $1)}' \
  | db.execute



thanks,
Hamish



  
___
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

Re: [GRASS-user] POW() in SQLite?

2010-03-01 Thread Rich Shepard 

On Mon, 1 Mar 2010, Hamish wrote:


I am trying to use POW(x,n) with SQLite but it fails:


Hamish,

  Mathematical functions such as POW() are not part of SQL. When you look at
what appear to be mathematical functions, e.g., ABS(). MIN(), MAX(), they
are actually string manipulations.

  SQLite stores most values as text strings so this is not surprising.

  I'd manipulate those values first, then pass them to SQLite.

Rich
___
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

Re: [GRASS-user] POW() in SQLite?

2010-03-01 Thread Glynn Clements 

Hamish wrote:

 I am trying to use POW(x,n) with SQLite but it fails:
 
 G65 v.db.select mapname column=POW(length,3)
 DBMI-SQLite driver error:
 Error in sqlite3_prepare():SELECT POW(length,3) FROM mapname
 no such function: POW

Nope; not in SQLite:

http://www.sqlite.org/lang_corefunc.html

 ERROR: Unable to open select cursor
 
 
 Similar problem if I try x^n:
 ...
 unrecognized token: ^

SQLite doesn't have a power operator:

http://www.sqlite.org/lang_expr.html#binaryops

 this random webhit suggests that it should be possible:
   http://osdir.com/ml/sqlite-users/2009-03/msg00248.html

That says:

 * Mathematical SQL Functions - The following mathematical SQL functions are
 available in addition to the SQLite default: ACOS(), ASIN(), ATAN(), ATAN(),
 ATAN2(), CEIL(), CEILING(), COS(), COT(), DEGREES(), EXP(), FLOOR(), LN(),
 LOG(), LOG(), LOG2(), LOG10(), MOD(), PI(), POW(), RADIANS(), SIGN(), SIN(),
 SQRT(), TAN(), TRUNCATE().

Note: in addition to the SQLite default. IOW, those functions are
added by SQLiteSpy, and are not part of SQLite.

-- 
Glynn Clements gl...@gclements.plus.com
___
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user