In my database, the collation was originally utf8_general_ci. However, I noticed that utf8_unicode_ci is necessary because of better sorting accuracy.
So I exported all database using phpmyadmin and checked that the word "COLLATION" does not appear in the exported sql file (except for only 2 times in one table where it is set to binary) so generally this script is collation agnostic and should not imply any specific collation when importing but use database default.
After dropping all tables, the database collation was changed to utf8_unicode_ci and then the import script was run from phpmyadmin. But as a result, all tables and all columns are shown again with utf8_general_ci collation (and sorting is incorrect). Why?? And what to do to change it?
P.S. The export/import script contains commented line at the beginning:
/*!40101 SET #OLD_COLLATION_CONNECTION=##COLLATION_CONNECTION */;
I don't know if it has any impact while importing, but after opening mysql console, the command show variables like 'collation_connection'shows COLLATION_CONNECTION as cp852_general_ci.
However, in phpmyadmin->variables the variable 'collation_connection' is set to utf8_general_ci. But there is no way to change it.
That happens because the database export is setting the character set on every table, and such a clause comes with a default collation that depends on the character set, not on the collation of your connection. utf8_general_ci is the default collation for utf8.
You'll have to convert your tables with something like ALTER TABLE tablename CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci; or edit your database export if this is affordable.
As for the MySQL console: the command-line client is pretty much broken on Windows. It'll never support, display or read Unicode, and you're getting a per-connection collation for that client that matches your Windows so-called OEM character set for your locale. This is a Windows misfeature that's difficult to workaround in portable software. PHPMyAdmin uses a web server and doesn't suffer from this problem. I advise you to use a UNIX-like operating system like GNU/Linux for any serious work in any case, not just for this reason. As an added benefit, MySQL, Apache and your whole application stack perform better on Linux.
Related
I've recently noticed that, when ever I start a new WordPress project, my tables' collation automatically changes from utf8_unicode_ci (which I select when I create a new DB from phpMyAdmin) to utf8mb4_unicode_520_ci.
Also, I've noticed in phpMyAdmin under “General Settings” that server connection Collation defaults to utf8mb4_unicode_520_ci.
I'm running MySQL Server 5.7.17 and phpMyAdmin 4.6.6 on Ubuntu 17.04.
My questions are following:
Why is this happening?
If possible, how do I prevent this? Because of utf8mb4 I've experienced problems when migrating WP sites to an older MySQL server which does not support it.
Is point 2. advisable? Are there any benefits in using charset utf8mb4 over utf8, and collation utf8mb4_unicode_520_ci over utf8_unicode_ci?
In the past, there was only utf8 (aka utf8mb3); in the future, utf8mb4 will be the default character set. now utf8mb4 is the default character set.
In the past, _general_ci was the default collation; then _unicode_ci (Unicode 4.0) was better, then _unicode_520_ci (Unicode 5.20). In the future (MySQL 8.0), the default will be _0900_ci_ai (Unicode 9.0).
Meanwhile, the road is full of potholes generated by MySQL's past mistakes. And WP designers are driving in a big tank that does not notice the potholes.
MySQL 5.6 was a big pothole that swallowed up many a WP user because of a 767 limit on indexes together with WP indexes on the overly-long VARCHAR(255) and the possibility of using utf8mb4. You are well past it by having 5.7.17. (Your future move to 8.0 will be less bumpy.)
That is, newly created databases/tables/columns on 5.7.7+ should not experience the 767 problem, but things migrated from older versions (5.5.3+) may have issues, especially if something causes you to change to utf8mb4.
What to do? I'll probably run out of space trying to spell out all the options. So provide the history of the data, the upgrade path (if any), the current settings, the ROW_FORMAT of the tables, the CHARACTER SET and COLLATION of the columns, the output of SHOW VARIABLES LIKE 'char%';
Where should you be? For 5.7.7+, utf8mb4 and utf8mb4_unicode_520_ci wherever practical. That charset gives you Emoji and all of Chinese (utf8 does not). That collation is the best available, although you might be hard pressed to notice where it matters.
Note: the first part of the collation name is the only character set that it works with. That is utf8_unicode_ci does not work with utf8mb4.
For MySQL 8.0, there is a better collation than the one mentioned in the title. In general, simply use the default collation for the chosen charset (unless you have some compatibility issue of language-specific need).
I started working on a wordpress on my dev machine. mysql version is 5.6, and worpdress is 4.7 so its already using the utf8mb4_unicode_520_ci encoding if it detects its possible.
My problem is that on my hosting (mysql 5.5) utf8mb4_unicode_520_ci is not recognized as a valid encoding. So I'm trying to target utf8mb4_unicode_ci encoding as my hosting knows about this one, and if I understand correctly, this would - in opposition to going to utf8 - allow me to keep the 4 bytes.
I tried several different combinaison of encoding and collation set up for the db, but nothing successful (from here How to convert an entire MySQL database characterset and collation to UTF-8?).
I tried several combination of encoding and collation in the wp-config, but nothing.
Everything that is coming from the database (like post titles and post contents displays badly encoded char for all diatrics, anything else is displayed appropriately )
menu label from the database display incorrectly, where the hardcoded/translated label display correctly
I think I need to convert the actual content of the database, changing charset and collation does not seems to be enough.
I found this but it does not address my problem directly, or if it does I missed it.
Any help would be appreciated
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UPDATE :
here is the precise procedure I went through:
Initial situation:
I installed a wordpress (4.6.1) locally (on my dev machine, mysql 5.6.28).
I worked on the theme and plugin locally
(at this moment I have, locally, a database that is utf8_general_ci and tables that are utf8mb4_unicode_520_ci
Problem:
I want to deploy my wordpress on my hosting (mysql: 5.5 - db collation seems to be utf8mb4_unicode_ci).
I mysqldump the db locally, then try to import it on my hostings' phpmyadmin.
This gives error :
Unknown collation: 'utf8mb4_unicode_520_ci'
solution 1 change the tables charset to utf8mb4_unicode_ci:
On my hosting sql server, utf8mb4_unicode_520_ci is not available and I can't get a more recent version of mysql.
utf8mb4_unicode_ci seems like the closest and is available on my hosting sql server.
from various so question, I adapt a bash script to change charset and collation of my tables
for tbl in wp_sij2017_commentmeta wp_sij2017_comments wp_sij2017_cwa wp_sij2017_links wp_sij2017_options wp_sij2017_postmeta wp_sij2017_posts wp_sij2017_term_relationships wp_sij2017_term_taxonomy wp_sij2017_termmeta wp_sij2017_terms wp_sij2017_usermeta wp_sij2017_users wp_sij2017_woocommerce_api_keys wp_sij2017_woocommerce_attribute_taxonomies wp_sij2017_woocommerce_downloadable_product_permissions wp_sij2017_woocommerce_order_itemmeta wp_sij2017_woocommerce_order_items wp_sij2017_woocommerce_payment_tokenmeta wp_sij2017_woocommerce_payment_tokens wp_sij2017_woocommerce_sessions wp_sij2017_woocommerce_shipping_zone_locations wp_sij2017_woocommerce_shipping_zone_methods wp_sij2017_woocommerce_shipping_zones wp_sij2017_woocommerce_tax_rate_locations wp_sij2017_woocommerce_tax_rates; do
mysql --execute="ALTER TABLE wp_sij_2017_original_copy.${tbl} CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"
done
I run this script on the local db
I now have all my tables set to collation utf8mb4_unicode_ci
My db collation is still utf8
I mysqldump the db, then import it to my hosting and...
Import is successful.
I search and replace siteurl in the db.
I then visit the online website, I got SOME diatrics that renders a "question mark char"
Any text coming from the db has decoding issue AT SOME POINT
The source/html markup also has those "question mark char"
I have no idea where to look or what to do next
Clarification: CHARACTER SETs utf8 and utf8mb4 specify how characters are encoded into bytes. COLLATIONs *_unicode_*, etc, specify how those character compare.
The encoding for utf8mb4_unicode_ci and utf8mb4_unicode_520_ci are the same because they are encoded in the character set utf8mb4.
"database that is utf8_general_ci and tables that are utf8mb4_unicode_520_ci" -- that probably means that new tables in that database, unless specifically stated, will be CHARACTER SET utf8 COLLATION utf8_general_ci. That is the database setting is just a default for CREATE TABLE. Since your tables are already CHARACTER SET utf8mb4 COLLATION utf8mb4_unicode_520_ci, the database default is not relevant to them.
As long as the CHARACTER SET stays utf8mb4, no Emoji, Chinese, etc will be lost or otherwise mangled.
Do not use mysql40; it did not know about any CHARACTER SETs. Do not use CONVERT or CAST. Etc.
I assume the 520 is coming from the output of mysqldump? Do you have an editor that can handle a file that big? If so, simply edit it to change utf8mb4_unicode_520_ci to utf8mb4_unicode_ci throughout. Then load the dump. Problem solved?
Your fix
You did ALTER ... CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci on your local machine. That is probably an even better way -- since it will put your dev and prod machine in line with each other. That should have worked. Don't worry about what the "database" claims.
I'm find 'utf8mb4_unicode_520_ci' and replace with 'utf8mb4_unicode_ci' in .sql file.
Its simplest why to solve this.
I have a local webserver running on my pc to which I use for local development. I'm now at the stage of exporting the database and importing onto my hosted VPS.
When exporting then importing I get the following error!
1115 - Unknown character set: 'utf8mb4'
Can somebody point me in the right direction?
The error clearly states that you don't have utf8mb4 supported on your stage db server.
Cause: probably locally you have MySQL version 5.5.3 or greater, and on stage/hosted VPS you have MySQL server version less then 5.5.3
The utf8mb4 character sets was added in MySQL 5.5.3.
utf8mb4 was added because of a bug in MySQL's utf8 character set.
MySQL's handling of the utf8 character set only allows a maximum of 3
bytes for a single codepoint, which isn't enough to represent the
entirety of Unicode (Maximum codepoint = 0x10FFFF). Because they
didn't want to potentially break any stuff that relied on this buggy
behaviour, utf8mb4 was added. Documentation here.
Solution 1:
Simply upgrade your MySQL server to 5.5.3 (at-least) - for next time be conscious about the version you use locally, for stage, and for prod, all must have to be same.
A suggestion - in present the default character set should be utf8mb4.
Solution 2 (not recommended): Convert the current character set to utf8, and then export the data - it'll load ok.
Sometimes I get similar problems while using HeidiSQL which by default exports in utf8mb4 character encoding. Not all MySQL installations support this encoding and importing such data leads to similar error messages. My workaround then is to export data using phpMyAdmin, which exports in utf8. There are problably other tools and possible ways like manually editing dump file, converting it from utf8mb4 to utf8 (if needed) and changing SET NAMES utf8mb4 to SET NAMES utf8. Utf8mb4 is a superset of utf8, so if you're absolutely sure, that your data is just utf8, then you can simply change SET NAMES in dump file to utf8.
Open sql file by text editor find and replace all
utf8mb4 to utf8
Import again.
This helped me
ALTER TABLE your_table_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
This seems like I'm just missing something trivial, but I'm not able to change the collation of a table from Schema Default. Selecting anything from the dropdown just reverts to Schema Default.
I have utf8 - utf8_general_ci set as the schema collation, which I can change without issue.
However, even though the schema default is set to utf8_general_ci and the tables supposedly use the schema default, when I export the SQL CREATE script and import it in phpMyAdmin, the collation is set to latin1_swedish_ci.
The script itself contains a correct CREATE SCHEMA statement:
CREATE SCHEMA IF NOT EXISTS 'my_table' DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci ;
But the CREATE TABLE statements only include the engine assignment.
I'm using MySQL Workbench 6.0, and the server I'm using is running MySQL 5.5.34 and phpyMyAdmin 3.4.11.1. The server default collation is also utf8_general_ci.
EDIT: As I suspected, something stupid. I created the database via the cPanel beforehand rather than through the SQL script, and the default collation was set to latin1_swedish_ci.
However, that doesn't explain why I couldn't set specific collations on the tables in Workbench.
Collations when not given the way they're supposed to be given will certainly revert to Schema Default.
Where did you set the collation in MySQL Workbench actually? There are 2 places, one in modeling and one for live objects (existing db objects in a server).
If the latter, did you apply your changes?
Because mysql default settings are not quite Unicode friendly it can happen quite often to endup with a database with broken charset.
Usually you just want to reconfigure it to use utf8 character set and utf8_unicode_ci collation.
Which is the easiest command to do this for a given database?
Warning: do not post links to untested scripts, I tested at least 5 of them (written in bash/perl/php/python) and they all failed to repair a database where the collation was set correctly at database and table level but not at column level.
I managed to write a solution myself and published to:
https://gist.github.com/1068021
Notes:
mysqldump is borken, even if tell it to not include CHARSET it will include them if it i set at column level.
this solution does not assume a default charset at mysql-server level so it set it at database level and resets it to defaults for table and column level.
Feed free to post bugs or patches, I will try to solve them fast.