Since my texts are in Portuguese, there are many words with accent and other special characters, like: "coração", "hambúrguer", "São Paulo".
Normally, I treat these names in Python with the following function:
from unicodedata import normalize
def string_normalizer(text):
result = normalize("NFKD", text.lower()).encode("ASCII", "ignore").decode("ASCII")
return result.replace(" ", "-")
This would replace the blank spaces with '-', replace special characters and apply a lowercase convertion. The word "coração" would become "coracao", "São Paulo" would become "Sao Paulo" and so on. Now, I'm not sure what's the best way to do this in Redshift. My solution would be to apply multiple replaces, something like this:
replace(replace(replace(lower(column), 'á', 'a'), 'ç', 'c')...
Even though this works, it doesn't look like the best solution. Is there an easy way to normalize my string?
In Redshift, you can use the translate function to normalize a string. The translate function takes three arguments: the source string, the characters to replace, and the replacement characters. You can use this function to replace all the special characters in your string with their ASCII equivalent.
For example, the following query uses the translate function to replace all the special characters in a string with their ASCII equivalent. Additionally, spaces are replaced with "-" characters.
SELECT translate('São Paulo', ' áàãâäéèêëíìîïóòõôöúùûüçÁÀÃÄÉÈÊËÍÌÎÏÓÒÕÖÔÚÙÛÜÇ', '-aaaaaeeeeiiiiooooouuuucAAAAAEEEEIIIIOOOOOUUUUC')
This query would return the string "Sao Paulo". You can use the lower function to convert the string to lowercase.
Here's an example of how you could use these functions together to normalize a string:
SELECT lower(translate('São Paulo', ' áàãâäéèêëíìîïóòõôöúùûüçÁÀà ÄÉÈÊËÍÌÎÏÓÒÕÖÔÚÙÛÜÇ', '-aaaaaeeeeiiiiooooouuuucAAAAAEEEEIIIIOOOOOUUUUC'))
This query would return the string "sao-paulo".
Related
In Bigquery, I am trying to find a way to extract particular segments of a string based on how many dashes come before it. The number of total dashes in the string will always be the same. For example, I could be looking for the string after the second dash and before the third dash in the following string:
abc-defgh-hij-kl-mnop
Currently, I am using the following regex to extract, which counts the dashes from the back:
([^-]+)(?:-[^-]+){2}$
The problem is that if there is nothing in between the dashes, the regex doesn't work. For example, something like this returns null:
abc-defgh-hij--mnop
Is there a way to use regex to extract a string after a certain number of dashes and cut it off before the subsequent dash?
Thank you!
Below is for BigQuery Standrd SQL
The simplest way in your case is to use SPLIT and OFFSET as in below example
SELECT SPLIT(str, '-')[OFFSET(3)]
above will return empty string for abc-defgh-hij--mnop
to prevent error in case of calling non-existing element - better to use SAFE_OFFSET
SELECT SPLIT(str, '-')[SAFE_OFFSET(3)]
I want to judge if a positive number string is end with ".0", so I wrote the following sql:
select '12310' REGEXP '^[0-9]*\.0$'. The result is true however. I wonder why I got the result, since I use "\" before "." to escape.
So I write another one as select '1231.0' REGEXP '^[0-9]\d*\.0$', but this time the result is false.
Could anyone tell me the right pattern?
Dot (.) in regexp has special meaning (any character) and requires escaping if you want literally dot:
select '12310' REGEXP '^[0-9]*\\.0$';
Result:
false
Use double-slash to escape special characters in Hive. slash has special meaning and used for characters like \073 (semicolon), \n (newline), \t (tab), etc. This is why for escaping you need to use double-slash. Also for character class digit use \\d:
hive> select '12310.0' REGEXP '^\\d*?\\.0$';
OK
true
Also characters inside square brackets do not need double-slash escaping: [.] can be used instead of \\.
If you know it is a number string, why not just use:
select ( val like '%.0' )
You need regular expression if you want to validate that the string has digits everywhere else. But if you only need to check the last two characters, like is sufficient.
As for your question . is a wildcard in regular expressions. It matches any character.
When trying to remove all accents from a string in Oracle using the techniques described in this stackoverflow answer: how replace accented letter in a varchar2 column in oracle I’m getting mixed results.
select CONVERT('JUAN ROMÄN', 'US7ASCII') from dual;
Returns the original string but replaces characters with for example ñ by a question mark (probably because of the chosen charset - tests with different charsets led to different results).
Using the following technique:
select utl_raw.cast_to_varchar2(nlssort(NAME_USER, 'nls_sort=binary_ai')) from YOUR_TABLE;
Returns the complete string but also places a NUL value at the end of the string.
Is there a characterset that I can use with Spanish accents to get a correct result (the original string with the different accents removed); is there a way to avoid the NUL value in the utl_raw.cast_to_varchar2 technique?
Based on the comments the the replace char(0) seems to remove the NUL value. For example
select
upper(utl_raw.cast_to_varchar2((nlssort('this is áà ñew test','nls_sort=binary_ai')))) as test,
replace(upper(utl_raw.cast_to_varchar2((nlssort('this is áà ñew test','nls_sort=binary_ai')))),chr(0),'') as test2
from dual;
If possible I would however to have a more 'straightforward/simpler' solution.
You can use TRANSLATE(your_string, from_chars, to_chars) https://docs.oracle.com/cd/B19306_01/server.102/b14200/functions196.htm
Just put all chars with accents in from_chars string and their corresponding replacement chars in to_chars.
SQLITE Query question:
I have a query which returns string with the character '#' in it.
I would like to remove all characters after this specific character '#':
select field from mytable;
result :
text#othertext
text2#othertext
text3#othertext
So in my sample I would like to create a query which only returns :
text
text2
text3
I tried something with instr() to get the index, but instr() was not recognized as a function -> SQL Error: no such function: instr (probably old version of db . sqlite_version()-> 3.7.5).
Any hints howto achieve this ?
There are two approaches:
You can rtrim the string of all characters other than the # character.
This assumes, of course, that (a) there is only one # in the string; and (b) that you're dealing with simple strings (e.g. 7-bit ASCII) in which it is easy to list all the characters to be stripped.
You can use sqlite3_create_function to create your own rendition of INSTR. The specifics here will vary a bit upon how you're using
There's a URL field in my Hive DB that is of string type with this specific pattern:
/Cats-g294078-o303631-Maine_Coon_and_Tabby.html
and I would like to extract the two Cat "types" near the end of the string, with the result being something like:
mainecoontabby
Basically, I'd like to only extract - as one lowercase string - the Cat "types" which are always separated by '_ and _', preceded by '-', and followed by '.html'.
Is there a simple way to do this in HQL? I know HQL has limited functionality, otherwise I'd be using regexp or substring or something like that.
Thanks,
Clark
HQL does have a substr function as cited here: https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-StringFunctions
It returns the piece of a string starting at a value until the end (or for a particular length)
I'd also utilize the function locate to determine the location of the '-' and '_' in the URL.
As long as there are always three dashes and three underscores this should be pretty straight forward.
Might need case statements to determine number of dashes and underscores otherwise.
solution here...
LOWER(REGEXP_REPLACE(SUBSTRING(catString, LOCATE('-', catString, 19)+1), '(_to_)|(\.html)|_', ''))
Interestingly, the following did NOT work... JJFord3, any idea why?
LOWER(REGEXP_EXTRACT(SUBSTRING(FL.url, LOCATE('-', FL.url, 19)+1), '[^(_to_)|(\.html)|_]', 0))