这几天学习regexp写的小例子

记录一下，总感觉会用到，终于可以关电脑了

1.oracle学习中，经常会用到dual这张表，那么你试过select * from dual；？？？
语句

SELECT * FROM dual;

结果：

DUMMY
X

dummy：虚拟的，假的。
2. 要点：伪列 level，lpad 填充函数，connect by 子句

lpad( string, padded_length, [ pad_string ] )

lpad函数是Oracle数据库函数，lpad函数从左边对字符串使用指定的字符进行填充。从其字面意思也可以理解，l是left的简写，pad是填充的意思，所以lpad就是从左边填充的意思。

with x as
( select 'aa' chr from dual
union all
select 'bb' chr from dual)
select level ,chr,lpad( ' ' ,( LEVEL)* 5 , '-' )||chr other from x connect by level <= 2;

结果：

1   aa  ---- aa
2   aa  --------- aa
2   bb  --------- bb
1   bb  ---- bb
2   aa  --------- aa
2   bb  --------- bb

3.要点：connect by 子句，伪列 level，rownum
方法一

SELECT '爱我中国'||LEVEL||'-123456' FROM dual CONNECT BY LEVEL <=12;

结果：

爱我中国1-123456
爱我中国2-123456
爱我中国3-123456
爱我中国4-123456
爱我中国5-123456
爱我中国6-123456
爱我中国7-123456
爱我中国8-123456
爱我中国9-123456
爱我中国10-123456
爱我中国11-123456
爱我中国12-123456

方法二

SELECT '爱我中国'||ROWNUM||'-123456' FROM dual CONNECT BY ROWNUM <=12;

结果：

爱我中国1-123456
爱我中国2-123456
爱我中国3-123456
爱我中国4-123456
爱我中国5-123456
爱我中国6-123456
爱我中国7-123456
爱我中国8-123456
爱我中国9-123456
爱我中国10-123456
爱我中国11-123456
爱我中国12-123456

4.regexp用法练习
regexp用法学习

-- regexp_replace 
SELECT * FROM tmp;
SELECT t.STR,
       REGEXP_replace(t.STR,'020','gz'),
             REGEXP_replace(t.STR,'(\d{3})(\d{3})','<\2\1>',3)
FROM tmp t
WHERE t.ID = 'replace';

-- regexp_like 只能用于条件表达式
-- 查询id为like，同时字符串中包含以a|A开头，后面为数字的字符串
SELECT str FROM tmp t WHERE t.ID = 'like' AND regexp_like(t.STR,'a\d+','i');
-- 查询id为like，同时字符串开头为a|A，后面为数字的字符串
SELECT str FROM tmp t WHERE t.ID = 'like' AND regexp_like(t.STR,'^a\d+','i');
-- 
SELECT str FROM tmp t WHERE t.ID = 'like' AND regexp_like(t.STR,'^a\d+$','i');

-- ERGEXP_substr 字符串的截取
-- regexp_substr(source_char,pattern,position,occurrence)
-- regexp_substr(输入的字符串,正则表达式,标识从第几个字符开始匹配正则表达式,标识第几个匹配项)
SELECT t.STR,
       REGEXP_substr(t.STR,'[^,]+') str,
             regexp_substr(t.STR,'[^,]+',1,1) str,
             regexp_substr(t.STR,'[^,]+',1,2) str,
             regexp_substr(t.STR,'[^,]+',2,1) str,
             regexp_substr(t.STR,'[^,]+',2,2) str
FROM tmp t WHERE t.id =  'substr';             o

SELECT regexp_substr('123456789','\d',1,LEVEL) FROM dual CONNECT BY LEVEL <=9; 

-- regexp_instr 
-- regexp_instr(source_char,pattern,position,occurrence,return_option,match_parameter)
-- regexp_instr(输入的字符串，正则表达式，标识从第几个 字符 开始匹配正则表达式，标识第几个匹配项，返回项，匹配选项)

SELECT t.STR,
       regexp_instr(t.STR,'\.') ind,
             regexp_instr(t.STR,'\.',1,1) ind,
             REGEXP_instr(t.STR,'\.',1,2) ind,
             regexp_instr(t.STR,'\.',2,2) ind,
             regexp_instr(t.STR,'\.',5,2) ind
  FROM tmp t WHERE t.ID = 'instr'; 

------------------
select
  regexp_instr('192.168.0.1','\.',1,level) ind ,  -- 点号. 所在的位置
  regexp_instr('192.168.0.1','\d',1,level) ind    -- 每个数字的位置
from dual 
connect by level <=  9
-----------------
SELECT * FROM tmp t WHERE t.ID = 'instr';   
-----------------
SELECT /*t.STR,
       regexp_instr(t.STR,'\.',1,LEVEL) ind,
             regexp_instr(t.STR,'\d',1,LEVEL) ind,*/
             regexp_instr('192.168.0.1','\.',1,LEVEL) ind,
             regexp_instr('192.168.0.1','\d',1,LEVEL) ind,
             regexp_instr('192.168.0.1','\.',1,level) ind ,  -- 点号. 所在的位置
       regexp_instr('192.168.0.1','\d',1,level) ind,   -- 每个数字的位置
             LEVEL ROWSnum
FROM dual connect by level <=  9 ;  
--------------------
--一个有趣的玩具
--------------------

with sudoku as (
  select '020000080568179234090000010030040050040205090070080040050000060289634175010000020' as line
  from dual
),
tmp as (
  select regexp_substr(line,'\d{9}',1,level) row_line,
  level col
  from sudoku
  connect by level<=9
)
select regexp_replace( row_line ,'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)','\1 \2 \3 \4 \5 \6 \7 \8 \9') row_line
from tmp;
-----------------
select regexp_replace( row_line ,'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)','\1 \2 \3 \4 \5 \6 \7 \8 \9') row_line
FROM (
  select regexp_substr(line,'\d{9}',1,level) row_line,
  level col
  from (
  select '020000080568179234090000010030040050040205090070080040050000060289634175010000020' as line
  from dual)
  connect by level<=9
)