Thank you, I was wondering about adding a new constraint to an existing column that is currently holding data.
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
