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标题: oracle规则表达式趣题 (转) [打印本页]

作者: 张兴康 时间: 2020-7-23 17:31
标题: oracle规则表达式趣题 (转)
我有一张表记录了我们系统的登录记录：谁在什么时间从哪个主机登录

create table plch_logins (
when  timestamp(0) not null
, who varchar2(10) not null
, host  varchar2(30) not null
)
/

insert into plch_logins values (
timestamp '2016-02-01 10:00:10', 'John', '192.168.200.155'
)
/
insert into plch_logins values (
timestamp '2016-02-01 10:01:20', 'Jill', '10.0.0.42'
)
/
insert into plch_logins values (
timestamp '2016-02-01 10:02:30', 'Jack', 'pc42.plchhost.org'
)
/
insert into plch_logins values (
timestamp '2016-02-01 10:03:40', 'Jeff', 'cubic.com10.net'
)
/
insert into plch_logins values (
timestamp '2016-02-01 10:04:50', 'John', '192.168.200.155'
)
/
commit
/

有时候host是主机名字，有时候是IP地址。

我想知道每个主机的登录次数，但仅仅是对使用了IP地址的记录（而不是主机名字）。为此我有这个未完成的查询：

select host
   , count(*) logins
  from plch_logins
##REPLACE##
group by host
order by logins desc, host
/

哪些选项可用来取代##REPLACE##使得查询返回如下输出：

HOST                            LOGINS
------------------------------ ----------
192.168.200.155                      2
10.0.0.42                            1

(A)
where regexp_like(host, '^\d{1,3}(\.\d{1,3}){3}$')

(B)
where regexp_like(host, '^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$')

(C)
where regexp_like(host, '^\d\d?\d?\.\d\d?\d?\.\d\d?\d?\.\d\d?\d?$')

(D)
where regexp_like(
      host
      , '^[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.' ||
         '[[:digit:]]{1,3}\.[[:digit:]]{1,3}$'
   )

(E)
where regexp_substr(host, '^\d{1,3}(\.\d{1,3}){3}$') = host

(F)
where regexp_substr(host, '^\d{1,3}(\.\d{1,3}){3}$') is not null

(G)
where regexp_replace(host, '^\d{1,3}(\.\d{1,3}){3}$') is null

(H)
where instr(host, '.', 1, 1) between 2 and 4
and instr(host, '.', 1, 2) between instr(host, '.', 1, 1) + 2
                              and instr(host, '.', 1, 1) + 4
and instr(host, '.', 1, 3) between instr(host, '.', 1, 2) + 2
                              and instr(host, '.', 1, 2) + 4
and instr(host, '.', 1, 3) >= length(host) - 3
and instr(host, '.', 1, 4) = 0
and regexp_replace(host, '[^0123456789.]') = host

(I)
where instr(host, '.', 1, 1) between 2 and 4
and instr(host, '.', 1, 2) between instr(host, '.', 1, 1) + 2
                              and instr(host, '.', 1, 1) + 4
and instr(host, '.', 1, 3) between instr(host, '.', 1, 2) + 2
                              and instr(host, '.', 1, 2) + 4
and instr(host, '.', 1, 3) >= length(host) - 3
and instr(host, '.', 1, 4) = 0
and translate(
      host
      , '#' || translate(host, '#0123456789.', '#')
      , '#'
   ) = host

作者: 万望 时间: 2020-7-23 18:06
有点高深

作者: 张兴康 时间: 2020-7-24 13:17

万望发表于 2016-2-23 18:06
有点高深

慢慢看看总能看懂的

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