... SELECT b FROM mytable WHERE b = c will give you each row of the database which has identical b and c values. ... SELECT b FROM mytable AS m2 WHERE m2.b = m1.c will join the two views of the database together, so if mytable contains
b,c 1,2 2,3 the combined table for this subquery looks like: m1.b, m1.c, m2.b, m2.c 1,2,1,2 1,2,2,3 2,3,1,2 2,3,2,3 and it compares the middle two columns. Hope this helps, Dave. (PS: I'm not particularly knowledgeable about SQLite, so this might well be factually incorrect in important minor ways.) On Tue, Dec 4, 2012 at 1:26 AM, YAN HONG YE <yanhong...@mpsa.com> wrote: > SELECT c FROM mytable AS m1 WHERE NOT EXISTS (SELECT b FROM mytable AS > m2 WHERE m2.b = m1.c); > > SELECT c FROM mytable WHERE NOT EXISTS (SELECT b FROM mytable WHERE b = > c); > > > > > Sincerely, > Cordialement / Best Regards / Mit freundlichen Grüßen / Cordiali saluti ! > ___________________________________________ > --------------------------------------------------------------------------- > YE YANHONG/???- DASI/DRDS/ITVC/APFS/AVPM > PSA PEUGEOT CITROEN(CHINA) AUTOMOTIVE TRADE CO,. LTD SHANGHAI BRANCH > Tel: (+86) 21-2419 5488 Mobile:(+86) 13816808338 Fax: (+86) 21-2419 5004 > PSA internal call: 49 5488 > Email: yanhong...@mpsa.com<mailto:yanhong...@mpsa.com> > Address: 6th Floor, Building 1, No. 1528, Gumei Road, > Xuhui District, Shanghai > Post Code:200233 > ??: ?????????1528?A1?6? > > _______________________________________________ > 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
