索引系列六--索引特性之高度较低的验证体会

sqlplus ljb/ljb

drop table t1 purge;

drop table t2 purge;

drop table t3 purge;

drop table t4 purge;

drop table t5 purge;

drop table t6 purge;

drop table t7 purge;

create table t1 as select rownum as id ,rownum+1 as id2,rpad('*',1000,'*') as contents from dual connect by level<=1;

create table t2 as select rownum as id ,rownum+1 as id2,rpad('*',1000,'*') as contents from dual connect by level<=10;

create table t3 as select rownum as id ,rownum+1 as id2,rpad('*',1000,'*') as contents from dual connect by level<=100;

create table t4 as select rownum as id ,rownum+1 as id2,rpad('*',1000,'*') as contents from dual connect by level<=1000;

create table t5 as select rownum as id ,rownum+1 as id2,rpad('*',1000,'*') as contents from dual connect by level<=10000;

create table t6 as select rownum as id ,rownum+1 as id2,rpad('*',1000,'*') as contents from dual connect by level<=100000;

create table t7 as select rownum as id ,rownum+1 as id2,rpad('*',1000,'*') as contents from dual connect by level<=1000000;

create index idx_id_t1 on t1(id);

create index idx_id_t2 on t2(id);

create index idx_id_t3 on t3(id);

create index idx_id_t4 on t4(id);

create index idx_id_t5 on t5(id);

create index idx_id_t6 on t6(id);

create index idx_id_t7 on t7(id);

set linesize 1000

set autotrace off

select index_name,

blevel,

leaf_blocks,

num_rows,

distinct_keys,

clustering_factor

from user_ind_statistics

where table_name in( 'T1','T2','T3','T4','T5','T6','T7');

INDEX_NAME BLEVEL LEAF_BLOCKS NUM_ROWS DISTINCT_KEYS CLUSTERING_FACTOR

------------------ ----------- ---------- ------------- -----------------

IDX_ID_T1 0 1 1 1 1

IDX_ID_T2 0 1 10 10 2

IDX_ID_T3 0 1 100 100 15

IDX_ID_T4 1 3 1000 1000 143

IDX_ID_T5 1 21 10000 10000 1429

IDX_ID_T6 1 222 100000 100000 14286

IDX_ID_T7 2 2226 1000000 1000000 142858

已选择7行。