Oracle Database - Statistics - Columns

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1 - About

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.

3 - Management

3.1 - Gather

3.2 - Get

3.3 - Set

3.4 - Delete