索引与Null值对于Hints及执行计划的影响(二)
table t modify (username not null);
Table altered.
SQL> select /*+ index(t,i_t) */ * from t;
Execution Plan
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Plan hash value: 3593393735
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| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
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| 0 | SELECT STATEMENT | | 27 | 918 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 27 | 918 | 2 (0)| 00:00:01 |
| 2 | INDEX FULL SCAN | I_T | 27 | | 1 (0)| 00:00:01 |
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Note
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- dynamic sampling used for this statement
这就是Null值对于索引及查询的影响.