在使用implict update table 时，发现其中一个表一定要有唯一约束，否则会报错！但是oracle可以使用hints：/*+ BYPASS_UJVC*/ 屏蔽掉队唯一性的检查。

update (select /*+ BYPASS_UJVC */
          *
           from t_contract_template ct,
                (select distinct (t.id) vid,
                                 t.serial_number || '-' ||
                                 substr(pkg_map.org_company2segment(c.companyid),
                                        length(pkg_map.org_company2segment(c.companyid)) - 1,
                                        2) as vnum
                   FROM t_contract_template     t,
                        t_contract_template_ver v,
                        t_template_city         c
                  where t.id = v.template_id
                    and t.id = c.templateverid
                    and v.enforce = 7
                    and t.serial_number is not null
                    and INSTR(t.serial_number, '-') = 0
                    and length(t.serial_number) = 10) vv
          where ct.id = vv.vid) tct
    set tct.serial_number = tct.vnum;