I was wondering if anyone can help me with a regular expression - not my strongest point - to parse the WHERE part of a SQL statement. I need to extract the column names, either in "column" or "table.column" format. I'm using MySQL and PHP.
For example, parsing:
(table.column_a = '1') OR (table.column_a = '0'))
AND (date_column < '2014-07-03')
AND column_c LIKE '%my search string%'
should yield
table.column_a
table.column_b
date_column
column_c
Edit: clarification - the strings will be parsed in PHP with preg_* functions!
Thank you!
Assuming you are not doing this in SQL, you can use a regex like this:
[A-Za-z._]+(?=[ ]*(?:[<>=]|LIKE))
See regex demo.
This would work in Notepad++ and many languages.
Explanation
[A-Za-z._]+ matches the characters in your word (if you want to add digits, add 0-9
The lookahead (?=[ ]*(?:[<>=]|LIKE)) asserts that what follows is optional spaces (the brackets are optional, they make the space stand out), then one of the characters in this class [<>=] (an operator OR | LIKE
You can add operators inside [<>=], or tag them at the end with another alternation, e.g. |REGEXP
Reference
Lookahead and Lookbehind Zero-Length Assertions
Mastering Lookahead and Lookbehind
Related
I have two types of URL's which I would need to clean, they look like this:
["//xxx.com/se/something?SE_{ifmobile:MB}{ifnotmobile:DT}_A_B_C_D_E_F_G_H"]
["//www.xxx.com/se/car?p_color_car=White?SE_{ifmobile:MB}{ifnotmobile:DT}_A_B_C_D_E_F_G_H"]
The outcome I want is;
SE_{ifmobile:MB}{ifnotmobile:DT}_A_B_C_D_E_F_G_H"
I want to remove the brackets and everything up to SE, the URLS differ so I want to remove:
First URL
["//xxx.com/se/something?
Second URL:
["//www.xxx.com/se/car?p_color_car=White?
I can't get my head around it,I've tried this .*\/ . But it will still keep strings I don't want such as:
(1 url) =
something?
(2 url) car?p_color_car=White?
You can use
regexp_replace(FinalUrls, r'.*\?|"\]$', '')
See the regex demo
Details
.*\? - any zero or more chars other than line breakchars, as many as possible and then ? char
| - or
"\]$ - a "] substring at the end of the string.
Mind the regexp_replace syntax, you can't omit the replacement argument, see reference:
REGEXP_REPLACE(value, regexp, replacement)
Returns a STRING where all substrings of value that match regular
expression regexp are replaced with replacement.
You can use backslashed-escaped digits (\1 to \9) within the
replacement argument to insert text matching the corresponding
parenthesized group in the regexp pattern. Use \0 to refer to the
entire matching text.
we are using following SQL to identify several rows which contain only SPECIAL CHARACTERs 'F#C(!!'. But seems it's not capturing some SPECIAL CHARACTER like 'F#C(!!'. Script should capture only special characters. Could you please share the optimized script to use for this scenario case
when regexp_like(column_name '^[^a-zA-Z]*$') then 'number'
when regexp_like(column_name, '^[^g-zG-Z]*$') then 'hex'
else 'string'
end
Try removing the ^ and $ anchors from the regex pattern you are using with regexp_like:
select *
from your_table
where regexp_like(column_name, '[^a-zA-Z]');
The above logic would check for the presence of one or more characters which are not letters. If you instead want to check for non alphanumeric, then use [^A-Za-z0-9].
Hi may i know what does the below query means?
REGEXP_REPLACE(number,'[^'' ''-/0-9:-#A-Z''[''-`a-z{-~]', 'xy') ext_number
part 1
In terms of explaining what the function function call is doing:
It is a function call to analyse an input string 'number' with a regex (2nd argument) and replace any parts of the string which match a specific string. As for the name after the parenthesis I am not sure, but the documentation for the function is here
part 2
Sorry to be writing a question within an answer here but I cannot respond in comments yet (not enough rep)
Does this regex work? Unless sql uses different syntax this would appear to be a non-functional regex. There are some red flags, e.g:
The entire regex is wrapped in square parenthesis, indicating a set of characters but seems to predominantly hold an expression
There is a range indicator between a single quote and a character (invalid range: if a dash was required in the match it should be escaped with a '\' (backslash))
One set of square brackets is never closed
After some minor tweaks this regex is valid syntax:
^'' ''\-\/0-9:-#A-Z''[''-a-z{-~]`, but does not match anything I can think of, it is important to know what string is being examined/what the context is for the program in order to identify what the regex might be attempting to do
It seems like it is meant to replaces all ASCII control characters in the column or variable number with xy.
[] encloses a class of characters. Any character in that class matches. [^] negates that, hence all characters match, that are not in the class.
- is a range operator, e.g. a-z means all characters from a to z, like abc...xyz.
It seams like characters enclosed in ' should be escaped (The second ' is to escape the ' in the string itself.) At least this would make some sense. (But for none of the DBMS I found having a regexp_replace() function (Postgres, Oracle, DB2, MariaDB, MySQL), I found something in the docs, that would indicate this escape mechanism. They all use \, but maybe I missed something? Unfortunately you didn't tag which DBMS you're actually using!)
Now if you take an ASCII table you'll see, that the ranges in the expression make up all printable characters (counting space as printable) in groups from space to /, 0 to 9, : to #, etc.. Actually it might have been shorter to express it as '' ''-~, space to ~.
Given the negation, all these don't match. The ones left are from NUL to US and DEL. These match and get replaced by xy one by one.
I am using a replace function to add some quotes around a couple of keywords.
However, this replacement doesn't work for a few cases like the one below.
See example below.
This is the query:
replace(replace(aa.SourceQuery,'sequence','"sequence"'),'timestamp','"timestamp"')
Before:
select timestamp, SparkTimeStamp
from SparkRecordCounts
After:
select "timestamp", Spark"timestamp"
from SparkRecordCounts
However, I want it to be like:
select "timestamp", Sparktimestamp
from SparkRecordCounts
EDIT I wrote this before knowing what RDBMS you were using but have left it in case it helps someone else.
I think you are looking for word boundaries in your replacement, which are generally a job for regular expressions.
Oracle has one built in, called regexp_replace, and you could use something like this:
regexp_replace(aa.SourceQuery, '(^|\s|\W)timestamp($|\s|\W)', '\1"timestamp"\2')
The regular expression looks at the start for:
^ - the start of the line OR
\s - a space character OR
\W - a non-word character
It then matches timestamp, and must end with:
$ - the end of the line OR
\s - a space character OR
\W - a non-word character
Then, and only then, does it perform the replace. \1 and \2 are used to preserve what word boundary matched at the beginning and ending of the word.
I'm not sure how other databases handle regexp_replace, it looks like mysql can via a plugin like this but there may not be a native method.
SQL Server has a solution to something similar here
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