W dniu 2016-03-14 08:36:40 użytkownik Dmitry Yemanov dim...@users.sourceforge.net [firebird-support] <firebird-support@yahoogroups.com> napisał: 14.03.2016 10:32, liviuslivius wrote: > > simple table > CREATE TABLE XXX( > A INTEGER > , B INTEGER > , CONSTRAINT UK_XXX__A__B UNIQUE(A, B) > ) > commit; > SELECT * FROM dbo.XXX X WHERE X.A BETWEEN 2 AND 30 *AND* X.B BETWEEN 5 > AND 60 > Select Expression > -> Filter > -> Table "XXX" as "X" Access By ID > -> Bitmap > -> Index "UK_XXX__A__B" Range Scan (lower bound: *1/2*, > upper bound: *1/2*) > As you can see only A key is used but B key should be also used. > I am missing something? Yes, you do. If the first segment is matched for non-equality, then the following segments cannot be used. Dmitry._,_._
Hi Dmitry, Why? Index is a Tree? And if i found VALUE 2 in A key then i can fast find value 5 in sub key (leaf) You scan throught keys in A, and then in finded nodes you look for leafs in B reagards, Karol Bieniaszewski
