IF NOT EXISTS (SELECT * FROM SYS.COLUMNS WHERE NAME = 'CD_USU' AND OBJECT_ID = OBJECT_ID('EST_NF_SAI_VENDAS'))
begin
ALTER TABLE dbo.EST_NF_SAI_VENDAS ADD
	CD_USU int NOT NULL CONSTRAINT DF_EST_NF_SAI_VENDAS_CD_USU DEFAULT 1
end