SQL SERVER或oracl如何判断删除列

ORACLE:

BEGIN
  EXECUTE IMMEDIATE 'DROP TABLE CUX_PO_VENDORS';
EXCEPTION
  WHEN OTHERS THEN
    NULL;
END;

alter   table   Tablename   drop   column   column1  

alter   table   Tablename   add(column1   varchar2(20),column2   number(7,2)...)

SQL SERVER:

IF COL_LENGTH('SYSFORM012','BUSINESS_SCOPE') IS NULL
BEGIN
  ALTER TABLE SYSFORM012 ADD BUSINESS_SCOPE NVARCHAR(300);
END