索引扫描方式

(1) 索引唯一扫描(index unique scan)(2) 索引范围扫描(index range scan)(3) 索引全扫描(index full scan)(4) 索引快速扫描(index fast full scan)

create table fang(id number constraint pk primary key,name varchar2(10))begin   for i in 1..10000 loop   insert into fang values(i,i);   end loop;   commit；end;
(1) 索引唯一扫描(index unique scan)SQL> select * from fang where id=1;       ----主键或者唯一索引，返回一行时执行计划----------------------------------------------------------Plan hash value: 1490543307
SELECT STATEMENTTABLE ACCESS BY INDEX ROWIDINDEX UNIQUE SCAN(2) 索引范围扫描(index range scan)SQL> select * from fang where id<1;      ----范围条件时[/b]
执行计划SELECT STATEMENT  TABLE ACCESS BY INDEX ROWID|INDEX RANGE SCAN     (3) 索引全扫描(index full scan)SQL> select id from fang order by id; ----请求列在索引中，且返回结果要求排序[/b]
执行计划SELECT STATEMENT  INDEX FULL SCAN (4) 索引快速扫描(index fast full scan)   ----[/b]请求列在索引中，返回结果不用排序[/b]
执行计划SQL> select id from fang; SELECT STATEMENT     INDEX FAST FULL SCAN