Lecture 20_1:


   B-trees on non-unique attributes

   B-trees on multiple attributes

   create index s1idx on showstoppers (baker, episodeid) ;

Searching in such B-trees

   R(X,Y)

   Which nodes in the index to search:  index search selectivity

   Consecutive searches:
   
   X='A' and Y=3
   X='A' and 3<= Y <= 8

   'A'<= X <= 'C' AND Y= 3 -> searching only 'A'<= X <= 'C'  and find tuples
   that satisfy Y=3
  

   How many tuples you find in the index that satisfy the search condition

   selectivity of index