I have a table temp. I applied new character set and collation in MYSQL with following query:
ALTER TABLE temp CONVERT TO CHARACTER SET utf8 COLLATE utf8_bin;
Now I want to revert this back to what the table was before I changed the attributes. Is there a way I can do that?
Thanks for help in advance.
Not without knowing what the previous value was. I think the default charset for mysql is latin1 and the default collation is case-insensitive (latin1_swedish_ci for latin1)
Related
Here, In my table, I've one column name as description.
As per my error, I've tried many solutions from SO to change the collation type.
I've tried below collection
1) utf8mb4_unicode_ci
2) utf8_general_ci
Here, SHOW FULL COLUMNS FROM your_table;
Can anyone know what is the right collation for \'\\xC3\' this type of string?
To support full UTF-8 Unicode like for example emojis in your case it is the character À you should use utf8mb4 and utf8mb4_unicode_ci utf8 is outdated.
You can find a full explanation at https://mathiasbynens.be/notes/mysql-utf8mb4.
You can check the current collations of your table like this:
SHOW FULL COLUMNS FROM your_table;
I assume your description column has type TEXT otherwise you might need to change the type.
To alter the table default character set you can use:
ALTER TABLE your_table CONVERT TO CHARACTER SET utf8mb4;
But this does not change the collation of your column.
To change the collation of your column you should use:
ALTER TABLE your_table MODIFY description TEXT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
Try this first
ALTER TABLE your_database_name.your_table CONVERT TO CHARACTER SET utf8
OR If above solution won't work then do the following after connecting to your database
SET NAMES 'utf8';
SET CHARACTER SET utf8;
Here is the command I use:
ALTER TABLE <table_name> MODIFY <column_name> VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci;
It works well. Now I need to set utf8mb4_unicode_ci for a column (since currently characters are shown as ???). Anyway here is my new command:
ALTER TABLE <table_name> MODIFY <column_name> VARCHAR(255) CHARACTER SET utf8 COLLATE utf8mb4_unicode_ci;
But sadly MySQL throws:
ERROacR 1253 (42000): COLLATION 'utf8mb4_unicode_ci' is not valid for CHARACTER
Any idea?
The first part of the COLLATION name must match the CHARACTER SET name.
CHARACTER SET utf8mb4 is needed for Emoji and some Chinese characters.
Let's back up to the 'real' problem -- of question marks.
COLLATION refers to the rules of ordering and sorting, not encoding.
CHARACTER SET refers to the encoding. This should be consistent at all stages. Question Marks come from inconsistencies.
Trouble with UTF-8 characters; what I see is not what I stored points out that these are the likely suspects for Question Marks:
The bytes to be stored are not encoded as utf8/utf8mb4. Fix this.
The column in the database is not CHARACTER SET utf8mb4. Fix this if you need 4-byte UTF-8. (Use SHOW CREATE TABLE.)
Also, check that the connection during reading is UTF-8. The details depend on the application doing the connecting.
This worked for me:
ALTER TABLE <table_name> MODIFY <column_name> VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
Here is quetions about adding comment to column for MySQL. Can this comment be utf-8? Also what encoding MySQL uses for these columns by default?
Default character set and collation is set when the database is created
CREATE DATABASE mydb
DEFAULT CHARACTER SET utf8
DEFAULT COLLATE utf8_general_ci;
You can modify character set on a specific column like this
ALTER TABLE t MODIFY col1 CHAR(50) CHARACTER SET utf8;
I am trying to insert emoji's into mysql but it turns to question marks, I have changed mysql connection server collation, database collation , table collation and column collation. I used these to change the items
# For each database:
ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;
# For each table:
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
# For each column:
ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
I have done all these but emoji's in mysql still show question marks. Please what should I do to make mysql show the emojis. Thanks in advance
Little late to answer the question. But I hope it will be useful for others...
Above configuration makes the database tables to store utf8 encoded data. But, the database connection(JDBC) should be able to transfer the utf8 encoded data to client. For that the JDBC connection parameter charset should be set to utf8mb4.
The default encoding for inbound connections isn't set properly. DEFAULT CHARSET will return as utf8 however character_set_server will be something different.
So, Set default-character-set=utf8.
I have a utf8_general_ci database that I'm interested in converting to utf8_unicode_ci.
I've tried the following commands
ALTER DATABASE dbname CHARACTER SET utf8 COLLATE utf8_unicode_ci;
ALTER TABLE tbl_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci; (for every single table)
But that seems to change the charset for future data but doesn't convert the actual existing data from utf8_general_ci to utf8_unicode_ci.
Is there any way to convert the existing data to utf8_unicode_ci?
SHOW CREATE TABLE to see if it really set the CHARACTER SET and COLLATION on the columns, not just the defaults.
What was the CHARACTER SET before the ALTERs?
Do SELECT col, HEX(col) ... for some field that should have utf8 in it. This will help us determine if you really have utf8 in the table. The encoding for characters is different based on CHARACTER SET; the HEX helps discover such.
The ordering (WHERE, ORDER BY, etc) is controlled by COLLATION. The indexes probably had to be rebuilt based on your ALTER TABLE. Did big tables with indexes take a 'long' time to convert?
To actually see the difference between utf8_general_ci and utf8_unicode_ci, you need a "combining accent" or, more simply, the German ß versus ss:
mysql> SELECT 'ß' = 'ss' COLLATE utf8_general_ci,
'ß' = 'ss' COLLATE utf8_unicode_ci;
+-------------------------------------+-------------------------------------+
| 'ß' = 'ss' COLLATE utf8_general_ci | 'ß' = 'ss' COLLATE utf8_unicode_ci |
+-------------------------------------+-------------------------------------+
| 0 | 1 |
+-------------------------------------+-------------------------------------+
However, to test that in your tables, you would need to store those values and use WHERE or GROUP_CONCAT or something else to determine the equality.
What 'proof' do you have that the ALTERs failed to achieve the collation change?
(Addressing other comments: REPAIR should be irrelevant. CONVERT TO tells the ALTER to actually modify the data, so it should have done the desired action.)
You have to change the collation of every field in every table. As you say, the collation of the table is only the default value for fields created later, and the collation of the database is only the default value for tables created later.
As Lorenz Meyer said, the collation of the table is only the default value for fields created later and you need to set the defaults for the columns explicitly too.
Such a change looks like:
ALTER TABLE mytable CHANGE mycolumn mycolumn varchar(15) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci