create table check2(f1 varchar(20),f2 varchar(20));
creates a table with the default collation latin1_general_ci;
alter table check2 collate latin1_general_cs;
show full columns from check2;
shows the individual collation of the columns as 'latin1_general_ci'.
Then what is the effect of the alter table command?
To change the default character set and collation of a table including those of existing columns (note the convert to clause):
alter table <some_table> convert to character set utf8mb4 collate utf8mb4_unicode_ci;
Edited the answer, thanks to the prompting of some comments:
Should avoid recommending utf8. It's almost never what you want, and often leads to unexpected messes. The utf8 character set is not fully compatible with UTF-8. The utf8mb4 character set is what you want if you want UTF-8. – Rich Remer Mar 28 '18 at 23:41
and
That seems quite important, glad I read the comments and thanks #RichRemer . Nikki , I think you should edit that in your answer considering how many views this gets. See here https://dev.mysql.com/doc/refman/8.0/en/charset-unicode-utf8.html and here What is the difference between utf8mb4 and utf8 charsets in MySQL? – Paulpro Mar 12 at 17:46
MySQL has 4 levels of collation: server, database, table, column.
If you change the collation of the server, database or table, you don't change the setting for each column, but you change the default collations.
E.g if you change the default collation of a database, each new table you create in that database will use that collation, and if you change the default collation of a table, each column you create in that table will get that collation.
It sets the default collation for the table; if you create a new column, that should be collated with latin_general_ci -- I think. Try specifying the collation for the individual column and see if that works. MySQL has some really bizarre behavior in regards to the way it handles this.
may need to change the SCHEMA not only table
ALTER SCHEMA `<database name>` DEFAULT CHARACTER SET utf8mb4 DEFAULT COLLATE utf8mb4_unicode_ci ;
as Rich said - utf8mb4
(mariaDB 10)
Related
I noticed that my MODX database still uses latin1 character set in the database and in its tables. I would like to convert them to utf8mb4 and update collations accordingly.
Not totally sure how I should do this. Is this correct?
I alter every table to use utf8mb4 and utf8_unicode_ci?
I update the default character set and collation of the database.
Are indexes updated automatically? Is there something else I should be aware of?
A bonus question: what would be the most suitable latest utf8_unicode collation? Western languages should work.
Changing the default character sets of a table or a schema does not change the data in the column itself, it only changes the default to apply the next time you add a table or add a column to a table.
To convert current data, alter one table at a time:
ALTER TABLE <name> CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
The collation utf8mb4_0900_ai_ci is faster than earlier collations (at least according to the documentation), and it's the most current and accurate. This collation requires MySQL 8.0.
The most current collation in MySQL 5.7 is utf8_unicode_520_ci.
A table-conversion like this rebuilds the indexes, so there's nothing else you need to do.
For my databases, I used utf8mb4_unicode_ci with utf8mb4 character set as a default. This was a mistake and the folks who are using the databases I created are complaining about the collation. I need to convert it to utf8mb4_general_ci. Am I able to get away with just changing the DB using an alter statement such as:
ALTER DATABASE `#{database}` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
Or, will I need to change each individual table and deal with columns even though the charset is the same between the two collations? I can't seem to find definitive answers on this... I'm using MySQL 5.7.2x .
utf8mb4_unicode_520_ci is better than either of the collations you mentioned.
Why are they complaining? Perhaps JOINs are failing to use indexes. I would argue with them that the old tables should be changed.
ALTER DATABASE only sets up defaults for future tables. It will not do what you need.
ALTER TABLE ... CONVERT TO ... for each table is needed. See http://mysql.rjweb.org/doc.php/limits#767_limit_in_innodb_indexes for a similar ALTER. It provides a way to automatically generate all the ALTERs.
When I create a schema with collition utf8mb4_unicode_ci it becomes collition utf8mb4_0900_ai_ci (using Workbench). Even when the default settings of the server have collation utf8mb4_unicode_ci set it still becomes utf8mb4_0900_ai_ci.
CREATE SCHEMA `new_schema` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
This gives issues with foreign key constrains with another database while importing the database. The only way to fix it is to set the columns for the constrains manually one by one to collation utf8mb4_unicode_ci. Once I do that the constrains can be made.
Hope someone can explain why this happens and has an answer how to prevent it.
Best,
Ted
#Rick James, This is the output you requested:
The Workbench table inspector is not showing the collation that was set.
Run SHOW TABLE STATUS FROM your_schema; and you'll see the collation that was set. Or even in Workbench's Shema Inspector the correct collation is displayed.
This MySQL db was set up in Godaddy from installing WordPress. Things on the site were acting glitchy - swapping out theme and deactivating plugins didn't help, so I decided to take a look at the tables using phpmyAdmin.
I've never seen this before - all tables use utf8_general_ci (there are 13 tables), but at the bottom is the summary of everything and the collation shows latin1_swedish_ci, and not the utf8...
Seems like this shouldn't be. What can I do to make it all uniform, using the utf8... and not the latin1_swedish?
To help explain, SHOW CREATE TABLE gives you something like this:
CREATE TABLE `h2u` (
`c` varchar(9) CHARACTER SET utf8 DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
This says that the column c is utf8 (and some utf8 collation, probably utf8_general_ci), but the default for any other columns you might add is latin1 (and some latin1 collation, probably latin1_swedish_ci).
The CHARACTER SET and COLLATION on the column is what matters.
(It is sad that 3rd party software, while trying to be helpful, sometimes obscures useful info.)
Edit
I would guess from the picture that the default for the database is latin1 / latin1_swedish_ci and the default for each table is utf8 / utf8_general_ci. But the important thing is what the setting is for each column; the image does not show that.
The character set and collation for each column is important if you are using anything other than English text. Are you?
Yes, you have observed something strange. I am trying to say that it is probably not important, and very unlikely to cause any glitches other than with non-English text.
The following would have created output similar to the image:
CREATE DATABASE wp DEFAULT CHARACTER SET latin1;
CREATE TABLE wp_users (...) DEFAULT CHARACTER SET utf8; -- overriding the 'latin1'
I need to store some data in a MySQL table, but I got some problems with theese kind of characters: "ā" "æ" "ō" "ĕ" (and so on)
Till now I had theese data stored in a SQLlite database and it was great because all was good, but now I'm trying to export it in a MySQL DB, but the strange chars are stored not in the good way, even if I tried different char encode. (UTF-8, UTF-16, latin blah blah)
Does anyone know the correct way to do so?
thanks a lot!!
utf8 needs to be established in about 4 places.
The column(s) in the database -- Use SHOW CREATE TABLE to verify that they are explicitly set to utf8, or defaulted from the table definition. (It is not enough to change the database default.)
The connection between the client and the server. See SET NAMES utf8.
The bytes you have.
If you are displaying the text in a web page, check the <meta> tag.
Either you can switch to BLOB datatype, or if you insist on using TEXT/VARCHAR/CHAR then you need to change charset of your table and database as shown below.
CREATE DATABASE mydbname
CHARACTER SET utf8
COLLATE utf8_general_ci;
USE mydbname;
CREATE TABLE `mytable` (
`data` varchar(200) COLLATE utf8_unicode_ci NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
If you already have a database with utf8 charset and collation set to utf8_general_ci then you can simply alter your table as mentioned below:
ALTER TABLE `mytable` CHANGE `data` `data` VARCHAR(100)
CHARSET utf8 COLLATE utf8_general_ci DEFAULT '' NOT NULL;