SELECT * FROM PlanoContas

SELECT '001,001,' + RIGHT('000' + CAST(Codigo AS VARCHAR(3)), 3) AS CodigoFormatado
FROM PlanoContas;

Update PlanoContas 
set Codigo = a.CodigoFormatado
from (
SELECT '001,001,' + RIGHT('000' + CAST(Codigo AS VARCHAR(3)), 3) AS CodigoFormatado, Codigo
FROM PlanoContas) a
where a.Codigo = PlanoContas.Codigo

Update ContaPagar
set CodPlanoContas = a.CodigoFormatado
from (
SELECT '001,001,' + RIGHT('000' + CAST(Codigo AS VARCHAR(3)), 3) AS CodigoFormatado, CodPlanoContas
FROM ContaPagar) a
where a.CodPlanoContas = ContaPagar.CodPlanoContas

Update ContaPagar
set CodPlanoContas = a.CodigoFormatado
from (
SELECT '001,001,' + RIGHT('000' + CAST(Codigo_plc AS VARCHAR(3)), 3) AS CodigoFormatado, Codigo_plc
FROM Dados_db..PlanCn_tb) a
where a.Codigo_plc = ContaPagar.CodPlanoContas

Update ContaPagar
set CodPlanoContas = a.Codigo_plc
from (
SELECT Codigo_pag, Codigo_plc FROM Dados_db..Pagar_tb) a
where a.Codigo_pag = ContaPagar.Codigo

select * from ContaPagar
