Create a sequence and view, and create a sequence View

Create a sequence and view, and create a sequence View

The project must ensure that the order number is unique.

When the time is used to generate a large volume of business, there will still be duplicates.

Solution: Create a sequence table and view to retrieve from the View

CREATE SEQUENCE general_order_no_seq  INCREMENT 1  MINVALUE 1  MAXVALUE 9223372036854775807  START 1  CACHE 1;

CREATE OR REPLACE VIEW get_next_seq_view AS SELECT nextval('general_order_no_seq'::regclass) AS nextval;

Obtain:

ActiveRecord::Base.connection.execute('select * from get_next_seq_view;').first["nextval"].to_i

SQL code for creating a view

Amount
Create View
Create view VTest_A
AS
SELECT 'hello-world' AS

Query View
SELECT * FROM VTest_A

When creating a view, you can add an auto-increment column to the view.

Oracle uses Rownum

SQL Server uses ROW_NUMBER () OVER (ORDER BY (SELECT 0 ))

That is
Create view v _ VIEW name
SELECT
Rownum AS auto-incrementing sequence,
Other Columns
FROM
Table
WHERE
Condition

In this case, when you SELECT * FROM view, there is a column that is auto-incrementing in order.