SQL Server 2019

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CREATE TABLE tBookPrice(
     id INTEGER IDENTITY(1,1)
    ,name VARCHAR(256)
    ,code VARCHAR(256)
    ,price INTEGER
    ,calcId INTEGER
);

CREATE TABLE tBookPriceTmp(
     id INTEGER IDENTITY(1,1)
    ,name VARCHAR(256)
    ,price INTEGER
    ,code VARCHAR(256)
);

INSERT INTO tBookPrice(
     name
    ,code
    ,price
    ,calcId
)
VALUES
     ('Name 1','B56878',10,1)
    ,('Name 2','H56817',10,1)
    ,('Name 3','Y55617',10,1);

INSERT INTO tBookPriceTmp(
     name
    ,code
    ,price
)
VALUES
     ('Name 1','B56878',20)
    ,('Name 1','B56878',30)
    ,('Name 1','B56878',40);

INSERT INTO tBookPrice(
     name
    ,code
    ,price
    ,calcId
)
SELECT
     tData.name
    ,tData.code
    ,tData.price 
    ,(maxCode.maxId + 1) AS calcId
FROM tBookPriceTmp AS tData
INNER JOIN (
    SELECT
        code
        ,MAX(calcId) OVER (PARTITION BY code ORDER BY code ASC) AS maxId
    FROM tBookPrice
) AS maxCode
    ON tData.code = maxCode.code

SELECT *
FROM tBookPrice
ORDER BY code,calcId ASC

id	name	code	price	calcId
1	Name 1	B56878	10	1
4	Name 1	B56878	20	2
5	Name 1	B56878	30	2
6	Name 1	B56878	40	2
2	Name 2	H56817	10	1
3	Name 3	Y55617	10	1

id	name	code	price	calcId
1	Name 1	B56878	10	1
4	Name 1	B56878	20	2
5	Name 1	B56878	30	3
6	Name 1	B56878	40	4
2	Name 2	H56817	10	1
3	Name 3	Y55617	10	1