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

This view displays information on table and view columns that are guaranteed to return JSON data. These include:

• Columns of data type JSON

• Columns on which a check constraint containing the IS JSON condition is defined, where the IS JSON condition is always enforced. Such check constraints can contain only the IS JSON condition, or they can contain the IS JSON condition as part of a logical AND condition.

  For example, the following check constraints ensure that the IS JSON condition is always enforced and will therefore cause mycol to appear in the ALL_JSON_COLUMNS view:

  Copy
  mycol IS JSON
  mycol IS JSON AND LENGTH(mycol) > 100
  

  However, the following check constraint does not ensure that the IS JSON condition is enforced, because it is part of a logical OR condition, and will therefore cause mycol to be omitted from the ALL_JSON_COLUMNS view:

  Copy
  mycol IS JSON OR LENGTH(mycol) > 100
  

• View columns that are defined as the return value of a SQL function that returns JSON data. Such functions include:
  • TREAT ( expr AS JSON )
  • JSON_ARRAY, JSON_ARRAYAGG, JSON_MERGEPATCH, JSON_OBJECT, JSON_OBJECTAGG, JSON_QUERY, JSON_SERIALIZE, and JSON_TRANSFORM

  For example, in the following definition for view v1, column mycol is defined as the return value of the JSON_OBJECT function, which will therefore cause mycol to appear in the ALL_JSON_COLUMNS view:

  CopyCREATE TABLE t1 (text varchar2(100));
  CREATE VIEW v1 AS SELECT JSON_OBJECT(text) AS mycol FROM t1;
  

Related Views

• DBA_JSON_COLUMNS provides information on all JSON columns.

• USER_JSON_COLUMNS provides information on the JSON columns for which the user is the owner. This view does not display the OWNER column.