描述数据库DESCRIBE DATABASE

DESCRIBE DATABASE 语句返回现有数据库的元数据。DESCRIBE DATABASE statement returns the metadata of an existing database. 元数据信息包括数据库名称、数据库注释和文件系统上的数据库位置。The metadata information includes database name, database comment, and database location on the filesystem. 如果指定了可选 EXTENDED 选项,它将返回基本的元数据信息以及数据库属性。If the optional EXTENDED option is specified, it returns the basic metadata information along with the database properties. DATABASESCHEMA 是可互换的。The DATABASE and SCHEMA are interchangeable.

语法Syntax

{ DESC | DESCRIBE } DATABASE [ EXTENDED ] db_name

参数Parameters

  • db_name:现有数据库的名称或系统中的现有架构。db_name: The name of an existing database or an existing schema in the system. 如果该名称不存在,则会引发异常。If the name does not exist, an exception is thrown.

示例Examples

-- Create employees DATABASE
CREATE DATABASE employees COMMENT 'For software companies';

-- Describe employees DATABASE.
-- Returns Database Name, Description and Root location of the filesystem
-- for the employees DATABASE.
DESCRIBE DATABASE employees;
+-------------------------+-----------------------------+
|database_description_item|   database_description_value|
+-------------------------+-----------------------------+
|            Database Name|                    employees|
|              Description|       For software companies|
|                 Location|file:/you/Temp/employees.db  |
+-------------------------+-----------------------------+

-- Create employees DATABASE
CREATE DATABASE employees COMMENT 'For software companies';

-- Alter employees database to set DBPROPERTIES
ALTER DATABASE employees SET DBPROPERTIES ('Create-by' = 'Kevin', 'Create-date' = '09/01/2019');

-- Describe employees DATABASE with EXTENDED option to return additional database properties
DESCRIBE DATABASE EXTENDED employees;
+-------------------------+---------------------------------------------+
|database_description_item|                   database_description_value|
+-------------------------+---------------------------------------------+
|            Database Name|                                    employees|
|              Description|                       For software companies|
|                 Location|                file:/you/Temp/employees.db  |
|               Properties|((Create-by,kevin), (Create-date,09/01/2019))|
+-------------------------+---------------------------------------------+

-- Create deployment SCHEMA
CREATE SCHEMA deployment COMMENT 'Deployment environment';

-- Describe deployment, the DATABASE and SCHEMA are interchangeable, your meaning are the same.
DESC DATABASE deployment;
+-------------------------+------------------------------+
|database_description_item|database_description_value    |
+-------------------------+------------------------------+
|            Database Name|                    deployment|
|              Description|        Deployment environment|
|                 Location|file:/you/Temp/deployment.db  |
+-------------------------+------------------------------+