利用维对象来优化数据仓库的高级技巧
ASQL> SELECT /*+ all_rows */ D.F_YEAR,
2 SUM(F.M_AMOUNT1) M_AMMOUNT1,
3 SUM(F.M_AMOUNT2) M_AMMOUNT2
4 FROM TIME_DIM D, FACT_SALES F
5 WHERE D.F_DAY = F.F_DAY
6 GROUP BY D.F_YEAR
7 /
Execute Plan
SQLPLAN COST CARD KBYTE PS PE
------------------------------------------------------------ ---- ---- ----- -- --
0 SELECT STATEMENT Optimizer=HINT: ALL_ROWS 10 4 0
1 0 HASH (GROUP BY) 10 4 0
2 1 HASH JOIN 9 97 6
3 2 MAT_VIEW REWRITE ACCESS (FULL) OF MV_FACT_S... 3 34 2
4 2 VIEW OF 5 97 1
5 4 HASH (UNIQUE) 5 97 1
6 5 TABLE ACCESS (FULL) OF TIME_DIM (TABLE) 4 999 11
我不太会用语言表解说, 因此设计了这个实例来说明, 如果看不懂, 请多看几次吧!
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