Simplify CHS - Standard Tariff Mst [Import]

var tempcreation = @"CREATE TABLE #stdtariffmst
(
    id INT PRIMARY KEY IDENTITY(1,1),
    tariffname NVARCHAR(100) COLLATE DATABASE_DEFAULT,
    mainac NVARCHAR(6) COLLATE DATABASE_DEFAULT,
    subac NVARCHAR(6) COLLATE DATABASE_DEFAULT,
    taxind NVARCHAR(1) COLLATE DATABASE_DEFAULT,
    amount NUMERIC(10,2),
    cost NUMERIC(10,2),
    errorcode NVARCHAR(200) COLLATE DATABASE_DEFAULT,
    tariffcode NVARCHAR(6) COLLATE DATABASE_DEFAULT
)";

var inserttemp = @"INSERT INTO #stdtariffmst(tariffname,mainac,subac,taxind,amount,cost)
VALUES(UPPER(TRIM(@tariffname)),@mainac,@subac,UPPER(TRIM(@taxind)),@amount,@cost)";

/* -------------------- ERROR VALIDATIONS -------------------- */

// Error Code A - Duplicate Tariff Name within Excel
var errorcodeA = @"WITH A(tariffname) AS
(
    SELECT tariffname FROM #stdtariffmst
    GROUP BY tariffname
    HAVING COUNT(tariffname) > 1
)
UPDATE #stdtariffmst SET errorcode = COALESCE(RTRIM(errorcode),'') + ' A'
FROM A WHERE #stdtariffmst.tariffname = A.tariffname";

// Error Code B - Main A/c + Sub A/c must exist in account master
var errorcodeB = @"WITH A (mainac, subac) AS
(
    SELECT A1.mainac, A1.subac
    FROM accounts A
    INNER JOIN accounts1 A1 ON A.mainac = A1.mainac
    WHERE A.actype IN ('N','A','E','I','L') AND A1.IsActive = 'Y'
)
UPDATE ##stdtariffmst SET errorcode = COALESCE(RTRIM(errorcode),'') + ' B'
WHERE NOT EXISTS (SELECT mainac,subac FROM A WHERE ##stdtariffmst.mainac = A.mainac AND ##stdtariffmst.subac = A.subac)";

// Error Code C - Amount must be greater than Cost
var errorcodeC = @"UPDATE #stdtariffmst SET errorcode = COALESCE(RTRIM(errorcode),'') + ' C'
WHERE amount <= cost";

// Error Code  D - Only 1000 Tariff details can be imported.
var recordCntQuery = @"SELECT COUNT(*) AS cnt FROM #stdtariffmst;";

// Count of total error rows
var cnterror = @"SELECT COUNT(errorcode) AS CNT FROM #stdtariffmst
WHERE COALESCE(errorcode,'') != ''";

var tariffCodeQuery = @"WITH A (rowno,id) AS
(
    SELECT ROW_NUMBER() OVER (ORDER BY id) AS rowno,id FROM #stdtariffmst
)
UPDATE #stdtariffmst
SET tariffcode = FORMAT(A.rowno, '000000')
FROM A
WHERE #stdtariffmst.id = A.id";


// Query to fetch data after validations
var data = @"SELECT tariffcode,tariffname,amount,cost,
IIF(M.taxind = 'Y', 'Intrastate',IIF(M.taxind = 'N', 'Not Applicable', 'Interstate')) AS taxindname,
errorcode,IIF(A.achead = A1.acname, A.achead,
CONCAT_WS(',',A.achead,COALESCE(A1.acname,'Invalid Account Name'))) AS mainsubacname,
CONCAT(M.mainac,M.subac) AS mainsubacno
FROM #stdtariffmst M
LEFT JOIN accounts A ON M.mainac = A.mainac
LEFT JOIN accounts1 A1 ON M.mainac = A1.mainac AND M.subac = A1.subac
ORDER BY M.id ASC;";

var stdTariffMstInsert = @"INSERT INTO StdTariffMst (tariffcode,tariffname,amount,cost,taxind,taxgroup,
mainac,subac,chargetype,isactive)
SELECT tariffcode,tariffname,amount,cost,taxind,'NA' AS taxgroup,
mainac,subac,'F' AS chargetype,'Y' AS isactive
FROM #stdtariffmst;";

public class StdTariffMst
{
    public string ErrorCode { get; set; } = string.Empty; // New Column
}