crs = comd.ExecuteReader();
            return crs;
        }
        public DataSet getRS1(string sql)
        {
            DataSet ds = new DataSet();
            SqlDataAdapter da = new SqlDataAdapter();
            SqlConnection conn = this.getConnection();
            conn.Open();
            SqlCommand comd = conn.CreateCommand();
             = sql;
            da.SelectCommand = comd;
            da.Fill(ds);
            return ds;

        }
        public bool update(string sql)
        {
            SqlConnection conn = null;
            bool flag = false;
            conn = this.getConnection();
            SqlCommand comd = conn.CreateCommand();
             = sql;
            conn.Open();
            Thread.Sleep(1);
            int s = comd.ExecuteNonQuery();------>将截断字符串或二进制数据。语句已终止

            if (s <= 0)      
                flag = false;
            else
                flag = true;
            return flag;
        }
    }
}

你更新到数据库的字符串长度，超过了你数据库里限定的字符长度