收集扩展统计信息

参数依次是用户名，表明，列名

SQL> SELECT DBMS_STATS.CREATE_EXTENDED_STATS(USER, 'OPT_ACCT_FDIM', '(BUS_UNIT_SKID, ACCT_SKID)') FROM DUAL;

DBMS_STATS.CREATE_EXTENDED_STATS(USER,'OPT_ACCT_FDIM','(BUS_UNIT_SKID,ACCT_SKID)')

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SYS_STUJ8OD#X2IPA_B9_CH00B046T

SQL> SELECT DBMS_STATS.CREATE_EXTENDED_STATS(USER, 'OPT_ACTVY_FCT', '(BUS_UNIT_SKID, ACCT_PRMTN_SKID)') FROM DUAL;

DBMS_STATS.CREATE_EXTENDED_STATS(USER,'OPT_ACTVY_FCT','(BUS_UNIT_SKID,ACCT_PRMTN_SKID)')

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SYS_STU#CVQNKK5CCM0W2XEQWSRXSM

SELECT EXTENSION_NAME, EXTENSION
FROM   USER_STAT_EXTENSIONS
WHERE  TABLE_NAME='CUSTOMERS';

SQL> BEGIN

  2  DBMS_STATS.GATHER_TABLE_STATS(ownname => 'ADWG_OPTIMA_LA11',

  3  tabname => 'OPT_ACCT_FDIM',

  4  estimate_percent => 20,

  5  method_opt => 'for all columns size auto', 

  6  degree => 6,

  7  granularity => 'ALL',

  8  cascade=>TRUE

  9  );

 10  END;

 11  /

 --for all columns size auto 自动收集所有已经创建的column group的统计信息，如果需要创建新的column group，可以通过for columns()单独指定,例如：

EXEC DBMS_STATS.GATHER_TABLE_STATS('SH','CUSTOMERS',METHOD_OPT =>
'FOR ALL COLUMNS SIZE SKEWONLY
FOR COLUMNS (CUST_STATE_PROVINCE,COUNTRY_ID) SIZE SKEWONLY');

SQL> BEGIN

  2  DBMS_STATS.GATHER_TABLE_STATS(ownname => 'ADWG_OPTIMA_LA11',

  3  tabname => 'OPT_ACTVY_FCT',

  4  estimate_percent => 20,

  5  method_opt => 'for all columns size auto',

  6  degree => 6,

  7  granularity => 'ALL',

  8  cascade=>TRUE

  9  );

 10  END;

 11  /

PL/SQL procedure successfully completed.

删除 EXTENDED STATISTICS 

exec DBMS_STATS.DROP_EXTENDED_STATS (USER,'OPT_ACTVY_FCT','(BUS_UNIT_SKID, ACCT_PRMTN_SKID)');

创建基于表达式的拓展统计信息：

EXEC DBMS_STATS.GATHER_TABLE_STATS('sh','customers', method_opt =>
'FOR ALL COLUMNS SIZE SKEWONLY
FOR COLUMNS (LOWER(cust_state_province)) SIZE SKEWONLY');

也可以如下方式创建：

SELECT
DBMS_STATS.CREATE_EXTENDED_STATS(null,'customers','(LOWER(cust_state_province))')

FROM DUAL;

通过如下SQL查询拓展统计信息：

SELECT e.EXTENSION col_group, t.NUM_DISTINCT, t.HISTOGRAM
FROM   USER_STAT_EXTENSIONS e, USER_TAB_COL_STATISTICS t
WHERE  e.EXTENSION_NAME=t.COLUMN_NAME
AND    t.TABLE_NAME='CUSTOMERS';