I have an issue with unicode chars in an utf8mb4_general_ci table
SELECT * FROM `t1` WHERE c1='musca'
returns
musca
muşca
muşcă
What I would like to know is if this is a bug - sounds like it;
and if it affects searching - it might, or better said it should; I can't make the column unique index
Anything I should do so mysql would consider a and ă and s and ş as different entities? (probably a and â, t and ţ, and i and î as well, but I haven't checked).
Should I store unicode chars as â ă ş ţ î ?
I will need to retrieve the exact match of the user input.
Edited to add:
The answer is in the comments: I should collate the columns as utf8mb4_0900_as_cs as Madhur Bhaiya explained and demonstrated
You need COLLATION utf8_romanian_ci (or utf8mb4_romanian_ci) on the table columns in question. It is the only collation that treats those 5 characters as a separate 'letter'.
Reference: http://mysql.rjweb.org/utf8_collations.html
That is available in most versions of MySQL/MariaDB. There is no need for utf8mb4_0900_as_cs, which implies MySQL 8.0.
Related
I have my mySQL collation set to utf8_general_ci and despite the fact that my searches are diacritical-insensitive, ie LIKE 'test' returns 'tést', some searches which I would like to work fail, in particular LIKE 'host' will NOT return 'høst'.
Two questions: Is there a table that will show which characters are equivalent for a particular collation? Is there a way to set two characters as equivalents in mySQL as an override?
Thanks for the help.
To answer for first question you can referance collation-charts.org. It's kind of a pain because you will need to search each collation by hand, but it'll show you how they stack.
The relevant section in the MySQL manual can also be found here.
As far as your second question, I'm not sure if you can do an explicit override for a particular character; however you can create your own custom character set if you wish.
You can read about creating custom collations from the MySQL manual.
Is there any way to make search query accent insensitive?
the column's and table's collation are utf8_polish_ci and I don't want to change them.
example word : toruń
select * from pages where title like '%torun%'
It doesn't find "toruń". How can I do that?
You can change the collation at runtime in the sql query,
...where title like '%torun%' collate utf8_unicode_ci
but beware that changing the collation on the fly at runtime forgoes the possibility of mysql using an index, so performance on large tables may be terrible.
Or, you can copy the column to another column, such as searchable_title, but change the collation on it. It's actually common to do this type of stuff, where you copy data but have it in some slightly different form that's optimized for some specific workload/purpose. You can use triggers as a nice way to keep the duplicated columns in sync. This method has the potential to perform well, if indexed.
Note - Make sure that your db really has those characters and not html entities.
Also, the character set of your connection matters. The above assumes it's set to utf8, for example, via set names like set names utf8
If not, you need an introducer for the literal value
...where title like _utf8'%torun%' collate utf8_unicode_ci
and of course, the value in the single quotes must actually be utf8 encoded, even if the rest of the sql query isn't.
This wont work in extreme circumstances, but try to change the column collation to UFT8 utf8_unicode_ci. Then accented characters will be equal to their non-accented counterparts.
You could try SOUNDEX:
http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_soundex
This compares two string by how they sound. But this obviously delivers many more results.
Edit: if you're here because you're confused by the polish collation in MySQL, read this.
I'm trying to perform a full-text search on a table of polish cities and many of them contain accented characters. It's meant to be used in an ajax call for auto completion so it would be nice if the search was accent-insensitive. I've set the collation of the rows to ut8_polish_ci. Now, given the city "Zelów", I query the database like this
SELECT * FROMcitiesWHERE MATCH( city ) AGAINST ("zelow")
but to no avail. Mysql returns an empty result. I've tried different accents, tried adding different collations to the query but nothing helped. I'm not sure how I should approach this because accent-sensitivity seems to be poorly documented. Any ideas?
EDIT
So I found out that the case-insensitive full-text searches are performed only IN BOOLEAN MODE, so the correct query would be
SELECT * FROMcitiesWHERE MATCH( city ) AGAINST ( "zelow" IN BOOLEAN MODE )
Previously I thought otherwise due to a misleading comment on dev.mysql.com. There might be more to it but I'm just really confused right now.
Anyway, as mentioned in the comments below, I have UNIQUE index on the cities column so changing the collation of the table to accent-insensitive utf8_general_ci is out of the question.
I realized however, that the following query works quite well on a table with utf8_polish_ci collation:
SELECT * FROMcitiesWHERE city LIKE 'zelow' COLLATE utf8_general_ci
It would seem now that the most reasonable solution would be to do a full-text search in a similar fashion:
SELECT * FROMcitiesWHERE MATCH( city ) AGAINST ( 'zelow' IN BOOLEAN MODE ) COLLATE utf8_genral_ci
This however yields the following error:
#1253 - COLLATION 'utf8_general_ci' is not valid for CHARACTER SET 'binary'
This is really starting to get on my nerves. Might as well abandon full-text search in favour of a simple where-like approach but it doesn't seem sensible in a table with almost 50k records which will be intensively queried...
LAST EDIT
Ok, the thing with boolean mode was partly bullshit. Only partly because it indeed works as I said, however, on a utf8_general_ci it works the other way around. I'm utterly perplexed and have no will to study this issue further. I decided to drop the UNIQUE index (no further cities will be added anyway so no need to make a big deal out of it) and stick with the utf8_general_ci table collation. I appreciate all the help, it steered me in the right direction.
Change your collation to utf_general_ci. It ignores accent when searching and ordering but still stores them correctly.
MySQL is very flexible in the encoding/collation area, maybe too flexible. When changing your encoding/collation, make sure you are converting the table, not just changing the encoding/collation types.
ALTER TABLE tablename CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
You can also convert individual fields, so your table can have a collation setting of utf8_general_ci, but you can change one or more fields so they use some other collation. Base on the "binary" error you are seeing, it seems your text field might have a collation of UTF8-BIN (or be a blob). Can you post the result of CREATE TABLE?
Remember, the CHARACTER SET (encoding) is how the data is stored, the collation is how it is indexed. Not all combinations work.
My original problem, and question, might help a little:
Converting mysql tables from latin1 to utf8
If you try :
select * from cities where cityname like 'zelow'
Change your collation from binary to utf8_bin. utf8_bin should be compatible with utf8_general_ci, but will still allow you to store city names with differing accents.
We have issues with utf8-string comparisons in MySQL 5, regarding case and accents :
from what I gathered, what MySQL implements collations by considering that "groups of characters should be considered equal".
For example, in the utf8_unicode_ci collation, all the letters "EÉÈÊeéèê" are in the same box (together with other variants of "e").
So if you have a table containing ["video", "vidéo", "vidÉo", "vidÊo", "vidêo", "vidÈo", "vidèo", "vidEo"] (in a varchar column declared with ut8_general_ci collation) :
when asking MySQL to sort the rows according to this column, the sorting is random (MySQL does not enforce a sorting rule between "é" and "É" for example),
when asking MySQL to add a Unique Key on this column, it raises an error because it considers all the values are equal.
What setting can we fiddle with to fix these two points ?
PS : on a related note, I do not see any case sensitive collation for the utf8 charset. Did I miss something ?
[edit] I think my initial question still holds some interest, and I will leave it as is (and maybe one day get a positive answer).
It turned out, however, that our problems with string comparisons regarding accents was not linked to the collation of our text columns. It was linked to a configuration problem with the character_set_client parameter when talking with MySQL - which defaulted to latin1.
Here is the article that explained it all to us, and allowed us to fix the problem :
Getting out of MySQL character set hell
It is lengthy, but trust me, you need this length to explain both the problem and the fix.
Use collation that considers these characters to be distinct. Maybe utf8_bin (it's case sensitive, since it does binary comparison of characters)
http://dev.mysql.com/doc/refman/5.7/en/charset-unicode-sets.html
I set up a MyISAM table to do FULLTEXT searching.
I do not want searches to be case-sensitive.
My searches are along the lines of:
SELECT * FROM search WHERE MATCH (keywords) AGAINST ('+diversity +kitten' IN BOOLEAN MODE);
Let's say the keywords field I'm looking for has the value "my Diversity kitten".
I noticed the searches were case-sensitive.
I double-checked my collation on the search table, it was set to utf8_bin. D'oh!
I changed it to utf8_general_ci.
But my query is still case-sensitive!
Why?
Is there a server setting I need to change, too?
Is there something I need to do besides change the collation?
I did a "REPAIR TABLE search QUICK" to rebuild the FULLTEXT index, but that didn't do it either...
My searches are still case-sensitive. =(
Aha, figured it out for reals this time.
I believe my issue was using NaviCat to update the collation. I have an older version of NaviCat, maybe it was a bug or something.
Doing:
ALTER TABLE search CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
fixed it correctly.
Always use command line, kids! =)
Hmm - that behavior doesn't match the manual:
By default, the search is performed in
case-insensitive fashion. However, you
can perform a case-sensitive full-text
search by using a binary collation for
the indexed columns. For example, a
column that uses the latin1 character
set of can be assigned a collation of
latin1_bin to make it case sensitive
for full-text searches.
Which version of MySQL do you use? Can you provide some data that would allow replicating the problem on another machine?