This is related to
What are the characters that count as the same character under collation of UTF8 Unicode? And what VB.net function can be used to merge them?
This is how I plan to do this:
Use http://msdn.microsoft.com/en-us/library/dd374126%28v=vs.85%29.aspx to turn the string into
KD form.
Basically it'll turn most variation such as superscript into the normal number. Also it decompose tilda and accent into 2 characters.
Next step would be to remove all characters whose sole purpose is tildaing or accenting character.
How do I know which characters are like that? Which characters are just "composing characters"
How do I find such characters? After I find those, how do I get rid of it? Should I scan character by character and remove all such "combining characters?"
For example:
Character from 300 to 362 can be gotten rid off.
Then what?
Combining characters are listed in UnicodeData.txt as having a nonzero Canonical_Combining_Class, and a General_Category of Mn (Mark, nonspacing).
For each character in the string, call GetUnicodeCategory and check the UnicodeCategory for NonSpacingMark, SpacingCombiningMark or EnclosingMark.
You may be able to do it more efficiently using regex, eg Regex.Replace(str, "\p{M}", "").
Related
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 would like to have a regular expression to make an Oracle SQL REGEXP_LIKE query that checks
if a string starts with one alphanumeric character
if the string ends with one alphanumeric character
if the "body" of the string contains only alphanumeric character OR these authorized characters (written) : hyphen (dash), dot, apostrophe, space
if the authorised characters are NOT adjacent (to avoid something like "he--'''l..'-lo")
I started with this :
^[a-zA-Z0-9]+(a-zA-Z0-9\-\.'|([^\-\.'])\1)*[a-zA-Z0-9]$
I used backslash to escape assuming that dot and hyphen are metacharacters
I think this is what you want:
^[a-zA-Z0-9]+([-.' ][a-zA-Z0-9]|[a-zA-Z0-9])*\w?$
It looks for
at least 1 alphanumeric (alnum),
followed by
either an authorized character followed by an alphanumeric or just an alphanumeric, repeated any number of times (including 0).
optionally followed by
an alnum
This meets your specification. I'm not sure if starts with one alnum and ends with one alnum means that there must be at least 2 alnums, or if they can be the same. If there must be at least 2 of them, remove the last ? (which make the last alnum optional).
Regards
assuming you meant "authorised characters are NOT adjacent to each other"
try something along these lines
^[a-zA-Z0-9]+([a-zA-Z0-9]+[\-\.' ]?)*[a-zA-Z0-9]$
so that the repeating middle part always has one alphanumeric character followed by zero to one special characters.
I am trying to write a query which will tell me if certain record is having only the special characters. e.g- "%^&%&^%&" will error however "%HH678*(*))" is fine (as it's having alphanumeric values as well. I have written following query however, it's working fine only for English alphabets and numbers, if column is having some other characters like mandarin then also it's not giving expected value.Any help is highly appreciated.
SELECT * FROM test WHERE REGEXP_LIKE(sampletext, '[^]^A-Z^a-z^0-9^[^.^{^}^ ]' );
You may try this,
regexp_like(text, '^[^A-Za-z0-9]+$')
This would match the text only if the input text contains special chars ie, only chars which are not of letters or digits.
To detect strings containing only characters other than unaccented alphabetic, numeric, or white space characters try this:
regexp_like(text,'^[^a-zA-Z0-9[:space:]]+$')
If you don't think punctuation characters are special than add [:punct:] to the class of characters to ignore.
If you are looking for a specific set of characters you can use a character class of just those characters of interest, for example some common accented characters (note the lack of a leading ^ in the character class []:
regexp_like(text,'^[àèìòùÀÈÌÒÙáéíóúýÁÉÍÓÚÝâêîôûÂÊÎÔÛãñõÃÑÕäëïöüÿÄËÏÖÜŸçÇßØøÅåÆæœ]+$')
I am trying to write a search that queries our directory server running openldap.
The users are going to be searching using the first or last name of the person they're interested in.
I found a problem with accented characters (like áéíóú), because first and last names are written in Spanish, so while the proper way is Pérez it can be written for the sake of the search as Perez, without the accent.
If I use '(cn=*Perez*)' I get only the non-accented results.
If I use '(cn=*Pérez*)' I get only accented results.
If I use '(cn=~Perez)' I get weird results (or at least nothing I can use, because while the results contain both Perez and Pérez ocurrences, I also get some results that apparently have nothing to do with the query...
In Spanish this happens quite a lot... be it lazyness, be it whatever you want to call it, the fact is that for this kind of thing people tend NOT to write the accents because it's assumend all these searches work with both options (I guess since Google allowes it, everybody assumes it's supposed to work that way).
Other than updating the database and removing all accents and trimming them on the query... can you think of another solution?
You have your ~ and = swapped above. It should be (cn~=Perez). I still don't know how well that will work. Soundex has always been strange. Since many attributes are multi-valued including cn you could store a second value on the attribute that has the extended characters converted to their base versions. You would at least have the original value to still go off of when you needed it. You could also get real fancy and prefix the converted value with something and use the valuesReturnFilter to filter it out from your results.
#Sample object
dn:cn=Pérez,ou=x,dc=y
cn:Pérez
cn:{stripped}Perez
sn:Pérez
#etc.
Then modify your query to use an or expression.
(|(cn=Pérez)(cn={stripped}Perez))
And you would include a valuesReturnFilter that looked like
(!(cn={stripped}*))
See RFC3876 http://www.networksorcery.com/enp/rfc/rfc3876.txt for details. The method for adding a request control varies by what platform/library you are using to access the directory.
Search filters ("queries") are specified by RFC2254.
Encoding:
RFC2254
actually requires filters (indirectly defined) to be an
OCTET STRING, i.e. ASCII 8-byte String:
AttributeValue is OCTET STRING,
MatchingRuleId
and AttributeDescription
are LDAPString, LDAPString is an OCTET STRING.
The standard on escaping: Use "<ASCII HEX NUMBER>" to replace special characters
(https://www.rfc-editor.org/rfc/rfc4515#page-4, examples https://www.rfc-editor.org/rfc/rfc4515#page-5).
Quote:
The <valueencoding> rule ensures that the entire filter string is a
valid UTF-8 string and provides that the octets that represent the
ASCII characters "*" (ASCII 0x2a), "(" (ASCII 0x28), ")" (ASCII
0x29), "\" (ASCII 0x5c), and NUL (ASCII 0x00) are
represented as a backslash "\" (ASCII 0x5c) followed by the two hexadecimal digits
representing the value of the encoded octet.
Additionally, you should probably replace all characters that semantically modify the filter (RFC 4515's grammar gives a list), and do a Regex replace of non-ASCII characters with wildcards (*) to be sure. This will also help you with characters like "é".
I have a Sql statament using special character (ex: ('), (/), (&)) and I don't know how to write them in my VB.NET code. Please help me. Thanks.
Find out the Unicode code point for the character (from http://www.unicode.org) and then use ChrW to convert from the code point to the character. (To put this in another string, use concatenation. I'm somewhat surprised that VB doesn't have an escape sequence, but there we go.)
For example, for the Euro sign (U+20AC) you'd write:
Dim euro as Char = ChrW(&H20AC)
The advantage of this over putting the character directly into source code is that your source code stays "just pure ASCII" - which means you won't have any strange issues with any other program trying to read it, diff it, etc. The disadvantage is that it's harder to see the symbol in the code, of course.
The most common way seems to be to append a character of the form Chr(34)... 34 represents a double quote character. The character codes can be found from the windows program "charmap"... just windows/Run... and type charmap
If you are passing strings to be processed as SQL statement try doubling the characters for example.
"SELECT * FROM MyRecords WHERE MyRecords.MyKeyField = ""With a "" Quote"" "
The '' double works with the other special characters as well.
The ' character can be doubled up to allow it into a string e.g
lSQLSTatement = "Select * from temp where name = 'fred''s'"
Will search for all records where name = fred's
Three points:
1) The example characters you've given are not special characters. They're directly available on your keyboard. Just press the corresponding key.
2) To type characters that don't have a corresponding key on the keyboard, use this:
Alt + (the ASCII code number of the special character)
For example, to type ¿, press Alt and key in 168, which is the ASCII code for that special character.
You can use this method to type a special character in practically any program not just a VB.Net text editor.
3) What you probably looking for is what is called 'escaping' characters in a string. In your SQL query string, just place a \ before each of those characters. That should do.
Chr() is probably the most popular.
ChrW() can be used if you want to generate unicode characters
The ControlChars class contains some special and 'invisible' characters, plus the quote - for example, ControlChars.Quote