Oracle教程 2023-02-24

Oracle 视图 V$MAP_EXT_ELEMENT 官方解释，作用，如何使用详细说明

v$map_ext_element视图用于报告可用的外部表数据元列表，其中可以按表名称显示。V$MAP_EXT_ELEMENT可以看到特定外部表的名称、 schema、列名称和属性。

V$MAP_EXT_ELEMENT视图一般用于检查从外部表导入数据时，字段名称是否符合要求。

使用方法：

1、第一步，查看要查询表的数据元信息：

SELECT * FROM V$MAP_EXT_ELEMENT WHERE TABLE_NAME = ‘&表名’;

2、第二步，检查字段的数据属性及其值：

SELECT COLUMN_NAME, DATATYPE, DIGITS, DECIMAL, PRECISION, SCALE FROM V$MAP_EXT_ELEMENT WHERE TABLE_NAME = ‘&表名’ AND COLUMN_NAME = ‘&字段名’

V$MAP_EXT_ELEMENT displays supplementary information for all element mapping structures.

Column	Datatype	Description
`ELEM_IDX`	`NUMBER`	Index corresponding to the element
`NUM_ATTRB`	`NUMBER`	Number of Attributes (maximum is 5)
`ATTRB1_NAME`	`VARCHAR2(256)`	Name of the first Attribute
`ATTRB1_VAL`	`VARCHAR2(256)`	Value of the first attribute
`ATTRB2_NAME`	`VARCHAR2(256)`	Name of the second attribute
`ATTRB2_VAL`	`VARCHAR2(256)`	Value of the second attribute
`ATTRB3_NAME`	`VARCHAR2(256)`	Name of the third attribute
`ATTRB3_VAL`	`VARCHAR2(256)`	Value of the third attribute
`ATTRB4_NAME`	`VARCHAR2(256)`	Name of the fourth attribute
`ATTRB4_VAL`	`VARCHAR2(256)`	Value of the fourth attribute
`ATTRB5_NAME`	`VARCHAR2(256)`	Name of the fifth attribute
`ATTRB5_VAL`	`VARCHAR2(256)`	Value of the fifth attribute
`CON_ID`	`NUMBER`	The ID of the container to which the data pertains. Possible values include: `0`: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs. `1`: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data

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