MY_TAB_COL_STATISTICS

MY_TAB_COL_STATISTICS displays column statistics and histogram information extracted from MY_TAB_COLUMNS. All users can access this view. This view exists in both PG_CATALOG and SYS schema. The values of the LOW_VALUE and HIGH_VALUE columns in this view are different from those in database A due to different underlying table structures. When the value of LOW_VALUE is a high-frequency value, the value of LOW_VALUE in GaussDB is the second smallest value. When HIGH_VALUE is a high-frequency value, HIGH_VALUE of GaussDB is the second highest value. The value of the HISTOGRAM column is different from that of database A due to different statistical methods. GaussDB supports only two types of histograms: frequency and equi-width. The value of the SCOPE column in GaussDB is different from that in database A because GaussDB does not support global temporary table statistics. GaussDB database supports only local temporary table statistics, and the default value is SHARED.

**Table 1** MY_TAB_COL_STATISTICS columns
Name	Type	Description
table_name	character varying(128)	Table name.
column_name	character varying(128)	Column name.
num_distinct	numeric	Number of different values in a column.
low_value	raw	Low value in a column.
high_value	raw	High value in a column.
density	numeric	If there is a histogram on COLUMN_NAME, this column displays the selectivity of values in the histogram that span less than two endpoints. It does not represent the selectivity of values that span two or more endpoints. If no histogram is available on COLUMN_NAME, the value of this column is 1/NUM_DISTINCT.
num_nulls	numeric	Number of empty values in a column.
num_buckets	numeric	Number of buckets in the histogram of a column.
sample_size	numeric	Sample size used to analyze a column. Database restart is not supported. Otherwise, data loss will occur.
last_analyzed	timestamp(0) without time zone	Date when a column was last analyzed.
global_stats	character varying(3)	Not supported. Its value is NULL.
user_stats	character varying(3)	Not supported. Its value is NULL.
notes	character varying(99)	Not supported. Its value is NULL.
avg_col_len	numeric	Average length of a column, in bytes.
histogram	character varying(15)	Specifies whether the histogram exists and the type of the histogram if it exists. NONE: no histogram. FREQUENCY: frequency histogram. EQUI-WIDTH: equal-width histogram.
scope	character varying(7)	For statistics collected on any table other than global temporary tables, the value is SHARED (indicating that the statistics are shared among all sessions).
schema	character varying(64)	Name of the namespace to which the column belongs.