How could I do this SQL query?
Name Database: database_1
Column: Collation
Value: latin1_swedish_ci
I need the list of ALL "database_1" tables that have columns whose value contains the text %latin1%.
My final goal: I need to change these values in all the tables that contain this data, for example:
CHARACTER SET latin1 COLLATE latin1_swedish_ci
Change to:
CHARACTER SET utf8 COLLATE utf8_unicode_ci
I already have the consult ready for replacement:
ALTER TABLE `blog_sitemapconf` CHANGE `value` `value` VARCHAR(100) CHARACTER SET latin1 COLLATE latin1_english_ci NOT NULL DEFAULT '';
But I need to get the name of all tables that contain columns with
CHARACTER SET latin1 COLLATE latin1_swedish_ci
You can query this information from the information_schema.columns table:
SELECT table_name, column_name
FROM information_schema.columns
WHERE collation_name LIKE '%latin1%'
First, determine how you will be doing the charset conversion. If the table is correctly encoded in latin1, then this is the desired conversion:
ALTER TABLE tbl CONVERT TO CHARACTER SET utf8;
If, instead, you have utf8 bytes stored in latin1 columns, then the 'fix' is more complex.
However, that changes all CHAR/TEXT columns in the table. Is that OK?
If that is OK, then this will generate all the ALTERs.
SELECT DISTINCT
CONCAT("ALTER TABLE ", table_schema, ".", table_name,
" CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;")
FROM information_schema.columns
WHERE character_set = 'latin1'
AND table_schema NOT IN ('mysql', 'information_schema', 'performance_schema');
You can then copy/paste them into the mysql commandline tool.
If you need to change only individual columns, then the fix is difficult because the rest of the attributes of each column must be repeated. This is not easy to do in a query.
Related
I am developing with mariadb and Spring, JdbcTemplate.
At first, we made DB charset as utf8, but now we have to change it into utf8mb4 because of emojis.
Till now I update individual charset with query something like below.
ALTER TABLE WT_WORKS CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
ALTER TABLE WT_WORKS CHANGE WORKS_TITLE WORKS_TITLE VARCHAR(300) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
ALTER TABLE WT_WORKS CHANGE WORKS_DESC WORKS_DESC VARCHAR(500) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
However It is now efficient because of table relations. For example when I insert into WT_WORKS, also need to into WT_WRITERS. It looks impossible to find every tables and columns.
So I want to know change these at once.(Including Procedures and Functions). -- something like (v_name VARCHAR(10)) into (v_name VARCHAR(10) CHARSET utf8mb4).
Thanks for answer.
FYI. my my.cnf got follow settings
[client]
default-character-set=utf8mb4
[mysqld]
collation-server = utf8mb4_unicode_ci
character-set-server = utf8mb4
[client]
default-character-set = utf8mb4
SELECT DISTINCT TABLE_SCHEMA, TABLE_NAME
FROM information_schema.COLUMNS
WHERE CHARACTER_SET_NAME = 'utf8'
will list all the tables that still have some column set to utf8. When them, do ALTER TABLE .. CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci;
This should generate all the ALTERs you need:
SELECT DISTINCT
CONCAT(
"ALTER TABLE ", TABLE_SCHEMA, ".", TABLE_NAME,
" CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci;"
)
FROM information_schema.COLUMNS
WHERE CHARACTER_SET_NAME = 'utf8'
Then copy and paste them into the mysql command line tool.
Caveat: If you have some columns with charsets other than utf8, they will be blindly converted to utf8mb4. This would be bad for hex, ascii, etc., columns, such as country_code, uuid, md5, etc.
You could do something similar to change individual columns instead.
You do not need to do both.
I have a table which some of its columns has collation of utf8_bin. But I need to change them to utf8_unicode_ci.
I know this query for do it:
ALTER TABLE `shn_sho_cities` CHANGE `city_name` `city_name` VARCHAR( 100 ) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL ;
but as I want change all columns which have utf8_bin instead of writing a query for each column.
Is there any way which I could do this?
The following code will generate the required queries to change your collations, to utf8mb4 with utf8mb4_unicode_ci
SELECT CONCAT('ALTER TABLE `', TABLE_NAME,'` CONVERT TO CHARACTER SET
utf8mb4 COLLATE utf8mb4_unicode_ci;') AS mySQL
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA= "YOU-DB-NAME"
AND TABLE_TYPE="BASE TABLE"
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
I have an existing table and I want to convert the charset only for one specific column to utf-8.
I know that this command ALTER TABLE table_name CONVERT TO CHARACTER SET utf8 does it for the whole table but I'm looking for a column-specific command.
Is there a command for that?
Try this:
ALTER TABLE t MODIFY col1 CHAR(50) CHARACTER SET utf8mb4;
I share that, it can always help...
I modified a database recently; moving from utf8 to utf8mb4; here is the script that allowed me to generate the alters...
Generate SQL commands to alter the tables:
SELECT CONCAT("ALTER TABLE `",`TABLE_NAME`,"` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;")
FROM `information_schema`.`TABLES`
WHERE `TABLE_SCHEMA` = 'xxxx';
Generate SQL commands to alter each column:
SELECT CONCAT("ALTER TABLE `",`TABLE_NAME`,"` MODIFY `",`COLUMN_NAME`,"` ",COLUMN_TYPE," CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci ",IF(`IS_NULLABLE`='YES', 'NULL', 'NOT NULL')," ",IF(`COLUMN_DEFAULT` IS NOT NULL, CONCAT(" DEFAULT '", `COLUMN_DEFAULT`, "'"), ''),";")
FROM `information_schema`.`COLUMNS`
WHERE `TABLE_SCHEMA` = 'xxx' AND `TABLE_NAME` = 'xxxx' AND (`CHARACTER_SET_NAME` IS NOT NULL OR `COLLATION_NAME` IS NOT NULL);
Note that for foreign keys and primary keys that make a relationship, you will need to disable foregin key checks before modifying the column
SET FOREIGN_KEY_CHECKS=0;
and enable afterwards.
SET FOREIGN_KEY_CHECKS=1;
Below one worked for me.
ALTER TABLE table_name
MODIFY column_name VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci;
This one worked for me.
ALTER TABLE `table_name` CHANGE `column_name` `column_name` TEXT CHARACTER SET utf8 COLLATE utf8mb4_unicode_ci;
Our previous programmer set the wrong collation in a table (Mysql). He set it up with Latin collation, when it should be UTF8, and now I have issues. Every record with Chinese and Japan character turn to ??? character.
Is possible to change collation and get back the detail of character?
change database collation:
ALTER DATABASE <database_name> CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
change table collation:
ALTER TABLE <table_name> CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
change column collation:
ALTER TABLE <table_name> MODIFY <column_name> VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
What do the parts of utf8mb4_0900_ai_ci mean?
3 bytes -- utf8
4 bytes -- utf8mb4 (new)
v4.0 -- _unicode_
v5.20 -- _unicode_520_
v9.0 -- _0900_ (new)
_bin -- just compare the bits; don't consider case folding, accents, etc
_ci -- explicitly case insensitive (A=a) and implicitly accent insensitive (a=á)
_ai_ci -- explicitly case insensitive and accent insensitive
_as (etc) -- accent-sensitive (etc)
_bin -- simple, fast
_general_ci -- fails to compare multiletters; eg ss=ß, somewhat fast
... -- slower
_0900_ -- (8.0) much faster because of a rewrite
More info:
What are the differences between utf8_general_ci and utf8_unicode_ci?
What's the difference between utf8_general_ci and utf8_unicode_ci?
How to change collation of database, table, column?
What's the difference between utf8_general_ci and utf8_unicode_ci?
Here's how to change all databases/tables/columns. Run these queries and they will output all of the subsequent queries necessary to convert your entire database to character encoding utf8mb4 and collations to the MySQL 8 default of utf8mb4_0900_ai_ci. Hope this helps!
-- Change DATABASE Default Collation
SELECT
CONCAT('ALTER DATABASE `', SCHEMA_NAME,'` CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;')
FROM information_schema.SCHEMATA
WHERE SCHEMA_NAME
NOT IN ('sys','mysql','information_schema','performance_schema','innodb')
AND SCHEMA_NAME LIKE 'database_name';
Note that changing the schema default changes the default for new tables (and their columns). It does not modify existing columns of existing tables.
-- Change TABLE Collation / Char Set
SELECT
CONCAT('ALTER TABLE `', TABLE_SCHEMA, '`.`', TABLE_NAME, '` CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;')
FROM information_schema.TABLES
WHERE TABLE_SCHEMA
NOT IN ('sys','mysql','information_schema','performance_schema','innodb')
AND TABLE_TYPE = 'BASE TABLE'
AND TABLE_SCHEMA LIKE 'database_name';
Note that changing the table default changes the default for new columns. It does not modify existing columns on existing tables.
-- Change COLUMN Collation / Char Set
SELECT
CONCAT('ALTER TABLE `', TABLE_SCHEMA, '`.`', TABLE_NAME, '` MODIFY COLUMN `', COLUMN_NAME, '` ', COLUMN_TYPE,
IF(COLUMN_DEFAULT IS NOT NULL, CONCAT(' DEFAULT \'', COLUMN_DEFAULT, '\''), ''),
IF(IS_NULLABLE = 'YES', ' NULL ', ' NOT NULL '),
' COLLATE utf8mb4_0900_ai_ci;')
FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA
NOT IN ('sys','mysql','information_schema','performance_schema','innodb')
AND COLLATION_NAME IS NOT NULL
AND TABLE_SCHEMA LIKE 'database_name'
AND COLLATION_NAME = 'old_collation_name';
This changes the actual columns and the database behaviour on queries. It does not, however, convert the data if the data is not in a compatible collation/character set. See https://dev.mysql.com/blog-archive/mysql-8-0-collations-migrating-from-older-collations/ for details on migrating from older collations. We also assume here that your default values do not include a single quote - it would need to be escaped - and we ensure that COLLATION_NAME is not NULL to exclude columns with integers, timestamps etc.
We filter out the built-in system schemas such as sys and mysql in all three cases, as these should likely not be modified unless you have an explicit reason to do so.
Beware that in Mysql, the utf8 character set is only a subset of the real UTF8 character set. In order to save one byte of storage, the Mysql team decided to store only three bytes of a UTF8 characters instead of the full four-bytes. That means that some east asian language and emoji aren't fully supported. To make sure you can store all UTF8 characters, use the utf8mb4 data type, and utf8mb4_bin or utf8mb4_general_ci in Mysql.
Adding to what David Whittaker posted, I have created a query that generates the complete table and columns alter statement that will convert each table. It may be a good idea to run
SET SESSION group_concat_max_len = 100000;
first to make sure your group concat doesn't go over the very small limit as seen here.
SELECT a.table_name, concat('ALTER TABLE ', a.table_schema, '.', a.table_name, ' DEFAULT CHARACTER SET utf8mb4 DEFAULT COLLATE utf8mb4_unicode_ci, ',
group_concat(distinct(concat(' MODIFY ', column_name, ' ', column_type, ' CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci ', if (is_nullable = 'NO', ' NOT', ''), ' NULL ',
if (COLUMN_DEFAULT is not null, CONCAT(' DEFAULT \'', COLUMN_DEFAULT, '\''), ''), if (EXTRA != '', CONCAT(' ', EXTRA), '')))), ';') as alter_statement
FROM information_schema.columns a
INNER JOIN INFORMATION_SCHEMA.TABLES b ON a.TABLE_CATALOG = b.TABLE_CATALOG
AND a.TABLE_SCHEMA = b.TABLE_SCHEMA
AND a.TABLE_NAME = b.TABLE_NAME
AND b.table_type != 'view'
WHERE a.table_schema = ? and (collation_name = 'latin1_swedish_ci' or collation_name = 'utf8mb4_general_ci')
GROUP BY table_name;
A difference here between the previous answer is it was using utf8 instead of ut8mb4 and using t1.data_type with t1.CHARACTER_MAXIMUM_LENGTH didn't work for enums. Also, my query excludes views since those will have to altered separately.
I simply used a Perl script to return all these alters as an array and iterated over them, fixed the columns that were too long (generally they were varchar(256) when the data generally only had 20 characters in them so that was an easy fix).
I found some data was corrupted when altering from latin1 -> utf8mb4. It appeared to be utf8 encoded latin1 characters in columns would get goofed in the conversion. I simply held data from the columns I knew was going to be an issue in memory from before and after the alter and compared them and generated update statements to fix the data.
here describes the process well. However, some of the characters that didn't fit in latin space are gone forever. UTF-8 is a SUPERSET of latin1. Not the reverse. Most will fit in single byte space, but any undefined ones will not (check a list of latin1 - not all 256 characters are defined, depending on mysql's latin1 definition)