For columns with skewed data, you should collect histograms.
| Statistics Col | Description |
|---|---|
| NUM_DISTINCT | Number of distinct values (NDV) |
| LOW_VALUE | Low value |
| HIGH_VALUE | High value |
| NUM_NULLS | Number of nulls |
| NUM_BUCKETS | Number of buckets in histogram |
| AVG_COL_LEN | Average length (in bytes) |
| DENSITY | A decimal number between 0 and 1 that measures the selectivity of a column. Values close to 1 indicate that the column is unselective, whereas values close to 0 indicate that this column is more selective. |