Oracle教程 2023-04-03

Oracle 视图 ALL_USTATS 官方解释，作用，如何使用详细说明

Oracle视图 ALL_USTATS 按用户名返回一个数据库中指定表和索引统计信息的摘要。它汇总保存在USER_TAB_STATISTICS、USER_INDEX_STATISTICS用户空间表中的信息。

ALL_USTATS 是 ALL_TAB_STATISTICS 和 ALL_INDEX_STATISTICS 交集的统计信息，它创建出单一的、蓝图式的统计数据视图。依据 column_name 列，ALL_USTATS 表示是一列或索引项目。

ALL_USTATS 主要用于跟踪表和索引统计信息，这种统计信息可以在执行优化器决定时提供数据库引擎。因此，它可以帮助 Oracle 识别最佳执行路径以及最合理的功能的使用，使 SQL 申明自动优化和执行。

使用 ALL_USTATS 非常简单，用户只需要选择数据字典视图 ALL_USTATS 以获得表和索引的汇总统计数据。

例如，要查看某个表的统计信息，你可以执行以下 SQL 语句：

SELECT * FROM ALL_USTATS WHERE TABLE_NAME=’表名’;

ALL_USTATS describes the user-defined statistics collected on the tables and indexes accessible to the current user.

Related Views

DBA_USTATS describes the user-defined statistics collected on all tables and indexes in the database.
USER_USTATS describes the user-defined statistics collected on the tables and indexes owned by the current user.

Column	Datatype	Description
`OBJECT_OWNER`	`VARCHAR2(128)`	Owner of the table or index for which the statistics have been collected
`OBJECT_NAME`	`VARCHAR2(128)`	Name of the table or index for which the statistics have been collected
`PARTITION_NAME`	`VARCHAR2(128)`	Partition name of a table; NULL if the table is either nonpartitioned or the entry corresponds to the aggregate statistics for the table
`OBJECT_TYPE`	`VARCHAR2(6)`	Type of the object for which statistics have been collected: `INDEX` `COLUMN`
`ASSOCIATION`	`VARCHAR2(8)`	Statistics type association: `DIRECT` Direct association with the object for which the statistics have been collected `IMPLICIT` – Association for which the statistics have been collected is with the column type or index type, and the object is an instance of that column type or index type
`COLUMN_NAME`	`VARCHAR2(128)`	Column name, if `OBJECT_TYPE` is `COLUMN`, for which statistics have been collected
`STATSTYPE_SCHEMA`	`VARCHAR2(128)`	Schema of the statistics type which was used to collect the statistics
`STATSTYPE_NAME`	`VARCHAR2(128)`	Name of the statistics type which was used to collect statistics
`STATISTICS`	`RAW(2000)`	User-collected statistics for the object