If I have a column, say:
paths
And paths holds the absolute path to a file.
If I wanted, to remove n characters from the beginning and end of the records, for the entire path column - would this be possible?
Edit - example:
Lets say there are records in paths like so:
C:\Users\Alex\Documents\Files\File-1.txt
C:\Users\Alex\Documents\Files\File-2.txt
C:\Users\Alex\Documents\Files\File-3.txt
C:\Users\Alex\Documents\Files\File-4.txt
I would like to update the records to be:
Users\Alex\Documents\Files\File-1
Users\Alex\Documents\Files\File-2
Users\Alex\Documents\Files\File-3
Users\Alex\Documents\Files\File-4
So essentially removing n characters from the beginning and end of an entire column.
A general regex solution would be:
^(?:.{3})(.*)(?:.{4})$
# that is match exactly three chars in the beginning (non-capturing group)
# match everything up to the end of the string
# but as .* is sweet-tempered...
# it gives back the four characters in the end ($)
# your match is in the first group
See a demo on regex101.com
use this pattern and replace with nothing
^.{3}|.{4}$
Demo
As you tagged SQL which implies Standard SQL:
Answers to questions tagged with SQL should use ANSI SQL.
There's no need for anything more complicated than a SUBSTRING, you just need to calculate the number of characters you want to strip:
SUBSTRING(path FROM 4 FOR CHARACTER_LENGTH(path)-7)
This is also working as-is in PostgreSQL :)
Related
We have a problem with a regular expression on hive.
We need to exclude the numbers with +37 or 0037 at the beginning of the record (it could be a false result on the regex like) and without letters or space.
We're trying with this one:
regexp_like(tel_number,'^\+37|^0037+[a-zA-ZÀÈÌÒÙ ]')
but it doesn't work.
Edit: we want it to come out from the select as true (correct number) or false.
To exclude numbers which start with +01 0r +001 or +0001 and having only digits without spaces or letters:
... WHERE tel_number NOT rlike '^\\+0{1,3}1\\d+$'
Special characters like + and character classes like \d in Hive should be escaped using double-slash: \\+ and \\d.
The general question is, if you want to describe a malformed telephone number in your regex and exclude everything that matches the pattern or if you want to describe a well-formed telephone number and include everything that matches the pattern.
Which way to go, depends on your scenario. From what I understand of your requirements, adding "not starting with 0037 or +37" as a condition to a well-formed telephone number could be a good approach.
The pattern would be like this:
Your number can start with either + or 00: ^(\+|00)
It cannot be followed by a 37 which in regex can be expressed by the following set of alternatives:
a. It is followed first by a 3 then by anything but 7: 3[0-689]
b. It is followed first by anything but 3 then by any number: [0-24-9]\d
After that there is a sequence of numbers of undefined length (at least one) until the end of the string: \d+$
Putting everything together:
^(\+|00)(3[0-689]|[0-24-9]\d)\d+$
You can play with this regex here and see if this fits your needs: https://regex101.com/r/KK5rjE/3
Note: as leftjoin has pointed out: To use this regex in hive you might need to additionally escape the backslashes \ in the pattern.
You can use
regexp_like(tel_number,'^(?!\\+37|0037)\\+?\\d+$')
See the regex demo. Details:
^ - start of string
(?!\+37|0037) - a negative lookahead that fails the match if there is +37 or 0037 immediately to the right of the current location
\+? - an optional + sign
\d+ - one or more digits
$ - end of string.
Have strings containing 'q_' which I want to extract everything that comes after it. Some rows contain occurrence of q_ which I want everything that occurs after it. Example values in the column are:
prod-q_cat_trait_cat_social_issue
_prod-q_body_modification_graffiti
event_tickets
dappled_grey
_prod-q_cat_tech_support
What is wrong with my regular expression as I'm trying to remove the trailing '_' after q.
REGEXP_EXTRACT(queue_id, '[^q_]+$')
Is just returning
issue
I've also tried the split method:
SPLIT(queue_id, 'q_')[OFFSET(2)]
But this returns
Array index 2 is out of bounds (overflow)
Any suggestions. Thanks! (I am using Google Cloud SQL)
Using a capturing group, you may extract all after the first q_ with:
REGEXP_EXTRACT(queue_id, 'q_(.*)')
You may extract all after the last q_ with:
REGEXP_EXTRACT(queue_id, '.*q_(.*)')
See the regex demo #1 and regex demo #2.
Here, q_ finds the first occurrence of q_ and (.*) grabs the rest of the line into Group 1, and this is the value returned by REGEXP_EXTRACT. .* matches any 0+ chars other than line break chars as many as possible, that is why the second regex will start capturing the rest of the line after the last occurrence of q_.
Google Cloud SQL uses MySQL. I think the simplest method is substring_index():
select substring_index(queue_id, '-q_', -1)
Can you try this : q_([^q_]+)$? You'll have what you want in the first group.
Edit: this one match all the cases > (?(?<=-q_).*|^((?!-q_).)*$)
I want to retrieve file names from urls in sql.
for example:
Input:
url:
https://www.google.co.in/root/subdir/file.extension?p1=v1&p2=v2
https://www.abxdhcak.com/sitemap-companies.xml
then Output should be:
file.extension
sitemap-companies.xml
To match your expected output you can use REGEXP_REPLACE
REGEXP_REPLACE(txt, '^.*/|\?.*$') as rg
This does 2 things:
'^.*/'
This removes all characters up to and including the last forward-slash in the string.
'\?.*$'
This removes all characters after and including a question mark.
This may not work for all cases, but it works for the examples provided.
In Teradata, I'm looking for one regular expression pattern that would allow me to find a pattern of some numbers, then a space or maybe no space, and then 'SF'. It should return 7 in both cases below:
SELECT
REGEXP_INSTR('12345 1000SF', pattern),
REGEXP_INSTR('12345 1000 SF', pattern)
Or, my actual goal is to extract the 1000 in both cases if there's an easier way, probably using REGEXP_SUBSTR. More details are below if you need them.
I have a column that contains free text and I would like to extract the square footage. But, in some cases, there is a space between the number and 'SF' and in some cases there is not:
'other stuff 1000 SF'
'other stuff 1000SF'
I am trying to use the REGEXP_INSTR function to find the starting position. Through google, I have found the pattern for the first to be
'([0-9])+ SF'
When I try the pattern for the second, I try
'([0-9])+SF'
and I get the error
SELECT Failed. [2662] SUBSTR: string subscript out of bounds
I've also found an answer to a similar questions, but they don't work for Teradata. For example, I don't think you can use ? in Teradata.
The error message indicates you're using SUBSTR, not REGEXP_SUBSTR.
Try this:
RegExp_Substr(col, '[0-9]*(?= {0,1}SF)')
Find multiple digits followed by a single optional blank followed by SF and extract those digits.
I would pattern it like this:
\b(\d+)\s*[Ss][Ff]\b
\b # word boundary
(\d+) # 1 or more digits (captured)
\s* # 0 or more white-space characters
[Ss] # character class
[Ff] # character class
\b # word boundary
Demo
I have data like
http://www.linz.at/politik_verwaltung/32386.asp
stored in a text column. I thought a non-greedy extraction with
select substring(turl from '\..*?$') as ext from tdata
would give me .asp but instead it still ?greedely results in
.linz.at/politik_verwaltung/32386.asp
How can I only match against the last occurence of dot .?
Using Postgresql 9.3
\.[^.]*$ matches . followed by any number of non-dot characters followed by end-of-string:
# select substring('http://www.linz.at/politik_verwaltung/32386.asp'
from '\.[^.]*$');
substring
-----------
.asp
(1 row)
As for why the non-greedy quantifiers do not work here is that they still start matching as soon as possible while still trying to match as short as possible from there on.
Try this:
\.[\w]*$
Here is how it works:
all the word characters (\w), any numbers of them with *, between dot (\.) and the end of the string ($), with the last . itself.
Note: updated the answer, now will capture the strings ends with ..