2026-03-12 21:01:38

histograms/histogram_04.txt

@@ -0,0 +1,85 @@
+drop table T1 purge;
+
+create table T1 tablespace USERS as
+select 
+    rownum id,
+    case when rownum<10 then mod(rownum,4) else 999 end col1
+from   ( select 1 just_a_column
+         from DUAL
+         connect by level <= 20
+       )
+/
+
+
+
+drop table T2 purge;
+
+create table T2 tablespace USERS as
+select 
+    rownum id,
+    case when rownum<25 then mod(rownum,10) else 999 end col1
+from   ( select 1 just_a_column
+         from DUAL
+         connect by level <= 100
+       )
+/
+
+exec dbms_stats.gather_table_stats(user,'T1', method_opt=>'for all columns size 1');
+exec dbms_stats.gather_table_stats(user,'T2', method_opt=>'for all columns size 1');
+
+alter system flush shared_pool;
+
+drop table Q purge;
+create table Q as
+select /*+ GATHER_PLAN_STATISTICS */
+    T1.ID    id1
+  , T2.ID    id2
+  , T1.COL1  val
+from
+    T1,
+    T2
+where
+    T1.COL1=150
+  and T1.COL1=T2.COL1
+/
+
+
+select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST  +PEEKED_BINDS +PARALLEL +PARTITION +COST +BYTES'));
+
+
+exec dbms_stats.gather_table_stats(user,'T1', method_opt=>'for all columns size 1');
+exec dbms_stats.gather_table_stats(user,'T2', method_opt=>'for all columns size 1');
+
+exec dbms_stats.delete_table_stats('SYS','T1');
+exec dbms_stats.delete_table_stats('SYS','T2');
+
+exec dbms_stats.gather_table_stats(user,'T1', method_opt=>'for all columns size SKEWONLY');
+exec dbms_stats.gather_table_stats(user,'T2', method_opt=>'for all columns size SKEWONLY');
+
+
+alter system flush shared_pool;
+
+
+select /*+ GATHER_PLAN_STATISTICS */
+    T1.ID
+  , T2.ID
+  , T1.COL1
+from
+    T1,
+    T2
+where
+    T1.COL1=3
+  and T1.COL1=T2.COL1
+/
+
+
+select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST  +PEEKED_BINDS +PARALLEL +PARTITION +COST +BYTES'));
+
+
+@stats_col SYS T1 % % % %
+@stats_col SYS T2 % % % %
+
+
+@hist_cross_freq SYS T1 COL1 SYS T2 COL2
+
+