A view is a virtual table derived from one or more tables. It has the structure of a standard table but does not store data. Its content is defined by a query statement. Views fall into two categories: single-table views and multi-table views. Single-table views support queries and modifications that can change underlying table data. Multi-table views support queries only and do not modify table data. This topic describes how to create, rename, and delete views.
Prerequisites
You have logged on to a Hologres instance. For more information, see Connect to an instance.
Create a View
Log on to the Hologres management console.
In the top navigation bar, select a region.
Click Go to HoloWeb to open the HoloWeb developer page.
-
On the HoloWeb development page, click to enter the Metadata Management page. In the Logged-on Instances list, click the target database and then the target schema created under it. Right-click Views, and select Create View.
-
On the Create View page, configure the parameters.
Parameter
Description
Schema
The schema name.
Select the default public schema or a new schema name.
View Name
The name of the new Hologres view table.
Description
The description of the new Hologres view table.
Query Statement
In the editor box below Query Statement, enter the query statement. This can be a multi-table data query or a single-table data query.
-
Single-table views are typically used for queries and modifications, which can change table data. If the view data comes from a single table, modifying the view data updates the table data. Modifying table data also updates the corresponding view.
-
Multi-table views are generally used for queries and do not change table data. If the view data comes from multiple tables, modifying the view data is not supported.
NoteWhen using single-table views, modify view data carefully to avoid affecting business operations due to changes in the corresponding table data.
-
-
Click Submit in the upper-right corner of the page. The operational log below shows that the creation was successful. The created view appears in the corresponding directory on the left.
After creating the view, you can view its corresponding query statement and DDL statement, and preview the data on the view page.
Manage Views
-
Go to the HoloWeb development page. In the Logged-on Instances list on the Metadata Management interface, all logged-on instance names appear.
-
Search for views in the navigation pane on the left or find them in the Logged-on Instances list.
Perform the following operations:
-
Open View
To view and manage a view, right-click Open View to go to the view page.
Query View
Click Query View in the upper-right corner of the page. The page redirects to the Temporary Query page. In the editing area, enter the SQL statement and click Run to query the view. For more information about query operations, see SQL Window.
Edit View
To modify a view, click Edit View in the upper-right corner of the page. In the Query Statement area, edit the statement. Then click Submit in the upper-right corner of the page.
Refresh
After modifying the view content, click Refresh in the upper-right corner of the page to sync the information.
-
Delete View
Delete the current view. Right-click the target view and select Delete View. After confirming the information, click OK to complete the deletion.
-
Create and Delete Views Using SQL
Hologres also supports creating, viewing, and deleting views using SQL statements. For more information about SQL statements for views, see VIEW.