where C.col3 = 5 and A.col1 = B.col1 and A.col2 = C.col2 and B.col3 = 10; Execution Plan ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=CHOOSE (Cost=4 Card=1 Bytes=110) 1 0 HASH JOIN (Cost=4 Card=1 Bytes=110) 2 1 NESTED LOOPS (Cost=2 Card=1 Bytes=84) 3 2 TABLE ACCESS (FULL) OF 'C' (Cost=1 Card=1 Bytes=26) 4 2 TABLE ACCESS (FULL) OF 'A' (Cost=1 Card=82 Bytes=4756) 5 1 TABLE ACCESS (FULL) OF 'B' (Cost=1 Card=1 Bytes=26)
创建索引： create index inx_col12A on a(col1,col2); select A.col4 from C , A , B where C.col3 = 5 and A.col1 = B.col1 and A.col2 = C.col2 and B.col3 = 10; Execution Plan ---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=CHOOSE 1 0 MERGE JOIN 2 1 SORT (JOIN) 3 2 NESTED LOOPS 4 3 TABLE ACCESS (FULL) OF 'B' 5 3 TABLE ACCESS (BY INDEX ROWID) OF 'A' 6 5 INDEX (RANGE SCAN) OF 'INX_COL12A' (NON-UNIQUE) 7 1 SORT (JOIN) 8 7 TABLE ACCESS (FULL) OF 'C'
精品推荐