Oracle Database - Statistics - Columns

Card Puncher Data Processing

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.

Management

Gather

See Oracle Database - Statistics - Table

Get

ALL_TAB_COL_STATISTICS

Set

SET_COLUMN_STATS

Delete

DELETE_COLUMN_STATS





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