How to get number between special character in oracle - sql

Question

Can you help to get below output in oracle
File_20170902_Name.txt
File200_Name_20170902_1.txt
File400_20170902_Name_1.txt
File1_name_20170902.txt
I am expecting output like
20170902
20170902
20170902
20170902
Thanks in advance!!

Answer 1

Assuming that all the 8 digit numbers in your filenames are dates and are preceded by a _ and followed by an _ or .txt, you may use
select REGEXP_SUBSTR(files,'_(\d{8})(_|.txt)',1,1,NULL,1) as dt FROM t;
Demo
But some time number character will change like 6 (YYMMDD) character
This will match a sequence of 6 to 8 characters between _ or _ and .txt
REGEXP_SUBSTR(files,'_((\d{6,8}))(_|)',1,1,NULL,1)
Demo2
But, This isn't a comprehensive regex to match dates. i.e it could match digits like 20189999 or 180000 if they are part of filename. if you want to detect only dates, then you may have to combine them with methods specified here: Valid Date Checks in Oracle

Answer 2

Try this demo: http://sqlfiddle.com/#!4/c361c/4
select
regexp_replace(str,'.*(\d{8}).*','\1') as x
from table1
| X |
|----------|
| 20170902 |
| 20170902 |
| 20170902 |
| 20170902 |

Answer 3

Try this
create table tst (x varchar2(30));
insert into tst values ('File_20170902_Name.txt');
insert into tst values ('File200_Name_20170902_1.txt');
insert into tst values ('File400_20170902_Name_1.txt');
insert into tst values ('File1_name_20170902.txt');
Select x,
case
when substr(x, REGEXP_INSTR(x, '[^a-z|A-Z|0-9]') + 1, 1) between chr(48) and chr(57) Then
substr(x, REGEXP_INSTR(x, '[^a-z|A-Z|0-9]') + 1, REGEXP_INSTR(x, '[^a-z|A-Z|0-9]', 1, 2) - REGEXP_INSTR(x, '[^a-z|A-Z|0-9]') - 1)
else substr(x, REGEXP_INSTR(x, '[^a-z|A-Z|0-9]', 1, 2) + 1, REGEXP_INSTR(x, '[^a-z|A-Z|0-9]', 1, 3) - REGEXP_INSTR(x, '[^a-z|A-Z|0-9]', 1, 2) - 1)
end as t
From tst
Note: this query wont support if the number start after more than 2 special character like File_name_test_20170902.txt

Answer 4

The following both work about the same - the use a regular expression to make the basic selection, then make use of either a second call to REGEXP_SUBSTR or use "normal" string functions to get rid of the delimiters. I prefer the nested calls to REGEXP_SUBSTR over the use of TRANSLATE or REPLACE but you can take your pick:
Nested calls to REGEXP_SUBSTR:
WITH cteFiles AS (SELECT 'File_20170902_Name.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File200_Name_20170902_1.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File400_20170902_Name_1.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File1_name_20170902.txt' AS FILENAME FROM DUAL)
SELECT FILENAME, REGEXP_SUBSTR(REGEXP_SUBSTR(FILENAME, '_[0-9]+[_.]'), '[^_.]+') AS FINAL_NUMS
FROM cteFiles;
Using REPLACE:
WITH cteFiles AS (SELECT 'File_20170902_Name.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File200_Name_20170902_1.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File400_20170902_Name_1.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File1_name_20170902.txt' AS FILENAME FROM DUAL)
SELECT FILENAME, REPLACE(REPLACE(REGEXP_SUBSTR(FILENAME, '_[0-9]+[_.]'), '_', NULL), '.', NULL) AS FINAL_NUMS
FROM cteFiles;
Using TRANSLATE:
WITH cteFiles AS (SELECT 'File_20170902_Name.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File200_Name_20170902_1.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File400_20170902_Name_1.txt' AS FILENAME FROM DUAL UNION ALL
SELECT 'File1_name_20170902.txt' AS FILENAME FROM DUAL)
SELECT FILENAME, TRANSLATE(REGEXP_SUBSTR(FILENAME, '_[0-9]+[_.]'), '0123456789_.', '0123456789') AS FINAL_NUMS
FROM cteFiles;
SQLFiddle here
Best of luck.