oracle统计信息

1. create table t2 as select * from dba_objects;

  建索引：

create index idx_t2 on t2(object_id);

2.收集T2的表所有列和表上所有索引的统计信息：

exec dbms_stats.gather_table_stats(ownname=>'SYS',tabname=>'T2',estimate_percent=>100,cascade=>true,degree=>4);

degree表示并行度；

3.查看统计信息，脚本(soxi.txt)

Please enter Name of Table Owner (Null = SYS): SYS

Please enter Table Name to show Statistics for: T2

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Table Level

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Table Number       Empty Average Chain Average Global User    Sample Date

Name       of Rows Blocks       Blocks   Space Count Row Len Stats  Stats      Size MM-DD-YYYY

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

T2 87,361  1,246   0   0    0   98 YES    NO    87,361 07-07-2015

Column  Column       Distinct Number     Number Global User Sample Date

Name  Details Values Density Buckets      Nulls Stats  Stats   Size MM-DD-YYYY

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

OWNER  VARCHAR2(30)     31       0       1 0 YES  NO 87,361 07-07-2015

OBJECT_NAME  VARCHAR2(128) 52,669       0       1 0 YES  NO 87,361 07-07-2015

SUBOBJECT_NAME  VARCHAR2(30)    194       0       1     86,760 YES  NO    601 07-07-2015

OBJECT_ID  NUMBER(22) 87,361       0       1 0 YES  NO 87,361 07-07-2015

DATA_OBJECT_ID  NUMBER(22)  9,348       0       1     77,945 YES  NO  9,416 07-07-2015

OBJECT_TYPE  VARCHAR2(19)     45       0       1 0 YES  NO 87,361 07-07-2015

CREATED  DATE  1,244       0       1 0 YES  NO 87,361 07-07-2015

LAST_DDL_TIME  DATE  1,365       0       1 0 YES  NO 87,361 07-07-2015

TIMESTAMP  VARCHAR2(19)  1,440       0       1 0 YES  NO 87,361 07-07-2015

STATUS  VARCHAR2(7)      2       1       1 0 YES  NO 87,361 07-07-2015

TEMPORARY  VARCHAR2(1)      2       1       1 0 YES  NO 87,361 07-07-2015

GENERATED  VARCHAR2(1)      2       1       1 0 YES  NO 87,361 07-07-2015

SECONDARY  VARCHAR2(1)      2       1       1 0 YES  NO 87,361 07-07-2015

NAMESPACE  NUMBER(22)     21       0       1 0 YES  NO 87,361 07-07-2015

EDITION_NAME  VARCHAR2(30)      0       0       0     87,361 YES  NO 07-07-2015

     B       Average   Average

Index   Tree Leaf   Distinct    Number Leaf Blocks Data Blocks Cluster Global User      Sample Date

Name Unique  Level Blks       Keys   of Rows     Per Key   Per Key Factor Stats  Stats Size MM-DD-YYYY

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

IDX_T2 NONUNIQUE     1  194     87,361    87,361     1 1  1,385 YES    NO      87,361 07-07-2015

Index Column   Col Column

Name Name   Pos Details

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

IDX_T2 OBJECT_ID     1 NUMBER(22)

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Partition Level

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SubPartition Level

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