On Sun, Oct 10, 2010 at 3:08 AM, Fadhel Al-Hashim <fad...@gmail.com> wrote: > Thank you, > > I was wondering about adding a new constraint to an existing column that is > currently holding data.
As you can see from the syntax diagram, you can't just add a constraint. You have to add a column. You can always update the new constraint-full column with the value from the old constraint-less column. Or, recreate the table and copy data from the old table. > > On Sun, Oct 10, 2010 at 10:54 AM, P Kishor <punk.k...@gmail.com> wrote: > >> On Sun, Oct 10, 2010 at 2:45 AM, Fadhel Al-Hashim <fad...@gmail.com> >> wrote: >> > Good day, >> > >> > is it possible to Alter a table and add a unique constraint on one or >> more >> > columns? >> > >> >> See http://www.sqlite.org/lang_altertable.html >> >> In particular -- >> >> "The ADD COLUMN syntax is used to add a new column to an existing >> table. The new column is always appended to the end of the list of >> existing columns. The column-def rule defines the characteristics of >> the new column. The new column may take any of the forms permissible >> in a CREATE TABLE statement, with the following restrictions: >> >> The column may not have a PRIMARY KEY or UNIQUE constraint. >> The column may not have a default value of CURRENT_TIME, CURRENT_DATE, >> CURRENT_TIMESTAMP, or an expression in parentheses. >> If a NOT NULL constraint is specified, then the column must have a >> default value other than NULL. >> If foreign key constraints are enabled and a column with a REFERENCES >> clause is added, the column must have a default value of NULL. >> Note also that when adding a CHECK constraint, the CHECK constraint is >> not tested against preexisting rows of the table. This can result in a >> table that contains data that is in violation of the CHECK constraint. >> Future versions of SQLite might change to validate CHECK constraints >> as they are added." >> >> > thanks, >> > >> > fadhel >> > _______________________________________________ >> > sqlite-users mailing list >> > sqlite-users@sqlite.org >> > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >> > >> >> >> >> -- >> Puneet Kishor http://www.punkish.org >> Carbon Model http://carbonmodel.org >> Charter Member, Open Source Geospatial Foundation http://www.osgeo.org >> Science Commons Fellow, http://sciencecommons.org/about/whoweare/kishor >> Nelson Institute, UW-Madison http://www.nelson.wisc.edu >> ----------------------------------------------------------------------- >> Assertions are politics; backing up assertions with evidence is science >> ======================================================================= >> _______________________________________________ >> sqlite-users mailing list >> sqlite-users@sqlite.org >> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >> > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > -- Puneet Kishor http://www.punkish.org Carbon Model http://carbonmodel.org Charter Member, Open Source Geospatial Foundation http://www.osgeo.org Science Commons Fellow, http://sciencecommons.org/about/whoweare/kishor Nelson Institute, UW-Madison http://www.nelson.wisc.edu ----------------------------------------------------------------------- Assertions are politics; backing up assertions with evidence is science ======================================================================= _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
