create table scott.test01 as select * from dba_objects;<\/p>\n
update scott.test01 set object_name=object_type;
\ncommit;<\/p>\n
exec dbms_stats.gather_table_stats(‘SCOTT’,’TEST01′);<\/p>\n
select table_name,num_rows from dba_tables where owner = ‘SCOTT’ and table_name = ‘TEST01′;<\/p>\n
explain plan for select * from scott.test01 where object_name=’INDEX’ and object_type=’INDEX’;<\/p>\n
select * from table(dbms_xplan.display());<\/p>\n
select rpad(column_name, 30, ‘ ‘) column_name,
\n rpad(num_distinct, 8, ‘ ‘) num_distinct,
\n rpad(utl_raw.cast_to_varchar2(low_value), 15, ‘ ‘) low_value,
\n rpad(utl_raw.cast_to_varchar2(high_value), 10, ‘ ‘) high_value,
\n rpad(num_nulls, 8, ‘ ‘) num_nulls,
\n rpad(avg_col_len, 6, ‘ ‘) avg_col_len,
\n rpad(density, 20, ‘ ‘) density,
\n histogram
\n from dba_tab_col_statistics
\n where owner = ‘SCOTT’
\n and table_name = ‘TEST01’
\n and column_name in (‘OBJECT_NAME’, ‘OBJECT_TYPE’);<\/p>\n
exec dbms_stats.gather_table_stats(‘SCOTT’,’TEST01′,method_opt =>’for columns (object_name,object_type)’);<\/p>\n
explain plan for select * from scott.test01 where object_name=’INDEX’ and object_type=’INDEX’;<\/p>\n
select * from table(dbms_xplan.display());<\/p>\n
select count(*) from scott.test01 where object_name=’INDEX’ and object_type=’INDEX’;<\/p>\n
— \u5728\u524d\u9762\u6536\u96c6\u7edf\u8ba1\u4fe1\u606f\u76f4\u65b9\u56fe\u7684\u65f6\u5019\u4e5f\u53ef\u4ee5\u5efa\u7acb
\nselect dbms_stats.create_extended_stats(‘scott’,’test01′,'(object_name,object_type)’)from dual ;<\/p>\n
select * from dba_tab_cols a where table_name=’TEST01′;<\/p>\n
begin
\ndbms_stats.drop_extended_stats(
\nownname=>’SCOTT’,tabname=>’TEST01′,extension=>'(object_name,object_type)’
\n);
\nend;<\/p>\n","protected":false},"excerpt":{"rendered":"