1、达梦数据库:

   select 1 from syscolumns where id in(select id from sysobjects where UPPER(name)=UPPER('" + 表名+ "')) and UPPER(name)=UPPER ('"+字段名+"')

2、Oracle数据库:

   select 1 from user_tab_columns where UPPER(column_name)= UPPER('"+字段名+"') AND TABLE_NAME = UPPER('" + 表名+ "')

3、增加字段sql:

Oracle与达梦语法相同----   alter table  + 表名+  add +字段名+ varchar(255)