Oracle教程 2023-04-03

Oracle 视图 ALL_PART_COL_STATISTICS 官方解释，作用，如何使用详细说明

本站中文解释

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Oracle视图ALL_PART_COL_STATISTICS存储某分区表的每个分区的列的信息包括列的最小值、最大值、平均值等信息，可用于优化分区表的新数据进入较新的分区，实现更好的查询性能。

要使用ALL_PART_COL_STATISTICS视图，首先需要SQL修改权限，然后可以执行一个SELECT语句，查询某个表的分区信息，语法如下：

SELECT * FROM ALL_PART_COL_STATISTICS
WHERE table_schema = ‘Schema_name’
AND table_name = ‘table_name’

官方英文解释

ALL_PART_COL_STATISTICS displays column statistics and histogram information for the table partitions accessible to the current user.

Related Views

DBA_PART_COL_STATISTICS displays column statistics and histogram information for all table partitions in the database.
USER_PART_COL_STATISTICS displays column statistics and histogram information for the table partitions owned by the current user. This view does not display the OWNER column.

Column	Datatype	NULL	Description
`OWNER`	`VARCHAR2(128)`	`NOT NULL`	Owner of the partitioned table
`TABLE_NAME`	`VARCHAR2(128)`	`NOT NULL`	Name of the table
`PARTITION_NAME`	`VARCHAR2(128)`		Name of the table partition
`COLUMN_NAME`	`VARCHAR2(4000)`		Name of the column
`NUM_DISTINCT`	`NUMBER`		Number of distinct values in the column
`LOW_VALUE`	`RAW(1000)`		Low value in the column
`HIGH_VALUE`	`RAW(1000)`		High value in the column
`DENSITY`	`NUMBER`		If a histogram is available on `COLUMN_NAME`, then this column displays the selectivity of a value that spans fewer than 2 endpoints in the histogram. It does not represent the selectivity of values that span 2 or more endpoints. If a histogram is not available on `COLUMN_NAME`, then the value of this column is `1`/`NUM_DISTINCT`.
`NUM_NULLS`	`NUMBER`		Number of NULLs in the column
`NUM_BUCKETS`	`NUMBER`		Number of buckets in histogram for the column
`SAMPLE_SIZE`	`NUMBER`		Sample size used in analyzing the column
`LAST_ANALYZED`	`DATE`		Date on which the column was most recently analyzed
`GLOBAL_STATS`	`VARCHAR2(3)`		`GLOBAL_STATS` will be `YES` if statistics have been gathered or `NO` if statistics have been aggregated from subpartitions or have not been gathered
`USER_STATS`	`VARCHAR2(3)`		Indicates whether statistics were entered directly by the user (`YES`) or not (`NO`)
`NOTES`	`VARCHAR2(63)`		Describes some additional properties of the statistics. Possible values include: `INCREMENTAL`: Indicates that the column has synopses. `INCREMENTAL(HLL)`: Indicates that the column has synopses, and that the synopses are in the hyperloglog format introduced in Oracle Database 12c Release 2 (12.2.0.1). `INCREMENTAL(SAMPLING)`: Indicates that the column has synopses, and that the synopses are in the adaptive sampling format introduced in Oracle Database 11g Release 1 (11.1). This column can be used to determine whether synopses in the adaptive sampling format have been phased out entirely and purged properly.
`AVG_COL_LEN`	`NUMBER`		Average length of the column (in bytes)
`HISTOGRAM`	`VARCHAR2(15)`		Indicates existence/type of histogram: `NONE` `FREQUENCY` `HEIGHT BALANCED` `HYBRID` `TOP-FREQUENCY`

本站中文解释

官方英文解释

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