SQL Server 2017

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CREATE SEQUENCE MySequence
AS int
START WITH 1
INCREMENT BY 1;
CREATE TABLE MyTable
(
    MySeq varchar(20) CONSTRAINT [DF_MyTable_MySeq]
                      DEFAULT FORMAT((NEXT VALUE FOR MySequence), 'BK-000000#'),
    Foo   int,
    Bar   int,
    
    CONSTRAINT [PK_MyTable] PRIMARY KEY (MySeq)
);
INSERT INTO MyTable (Foo, Bar) 
VALUES (1,2),(2,3),(3,4),(5,6);
4 rows affected

SELECT * FROM MyTable;


MySeq
Foo
Bar


BK-0000001
1
2

BK-0000002
2
3

BK-0000003
3
4

BK-0000004
5
6