The following is an excerpt from an explain plan, could anybody explain the index range scan of DIAGNOSIS which returns 5 rows, but the corresponding table access returns 2688K rows, doesn't seem to make sense
| 10 | NESTED LOOPS SEMI | | 1 | 62 |
|* 11 | TABLE ACCESS BY INDEX ROWID BATCHED | EPISODES | 1 | 38 |
|* 12 | INDEX RANGE SCAN | IDX_EPISODES | 1 | |
|* 13 | TABLE ACCESS BY INDEX ROWID BATCHED | DIAGNOSIS | 2688K | 61M|
|* 14 | INDEX RANGE SCAN | IDX_DIAGNOSIS | 5 | |