Hướng dẫn update collation mysql

I am contributing here, as the OP asked:

How to change collation of database, table, column?

The selected answer just states it on table level.

Changing it database wide:

ALTER DATABASE  CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Changing it per table:

ALTER TABLE  CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Good practice is to change it at table level as it'll change it for columns as well. Changing for specific column is for any specific case.

Changing collation for a specific column:

ALTER TABLE  MODIFY  VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Nilpo

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answered Aug 17, 2016 at 11:51

Nabeel AhmedNabeel Ahmed

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6

You need to either convert each table individually:

ALTER TABLE mytable CONVERT TO CHARACTER SET utf8mb4 

(this will convert the columns just as well), or export the database with latin1 and import it back with utf8mb4.

terales

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answered Aug 18, 2009 at 14:14

QuassnoiQuassnoi

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12

You can run a php script.

                $value) {
                             mysql_query("ALTER TABLE $value CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci");
                       }}
                   echo "The collation of your database has been successfully changed!";
                ?>

answered Oct 4, 2012 at 6:23

hkaserahkasera

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0

To change collation for tables individually you can use,

ALTER TABLE mytable CONVERT TO CHARACTER SET utf8

To set default collation for the whole database,

ALTER DATABASE  `databasename` DEFAULT CHARACTER SET utf8 COLLATE utf8_bin

or else,

Goto PhpMyAdmin->Operations->Collation.

There you an find the select box which contains all the exsiting collations. So that here you can change your collation. So here after database table will follows this collation while you are creating new column . No need of select collation while creating new columns.

answered Jan 16, 2013 at 8:05

jeevajeeva

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1

The following query will generate ALTER queries that change the collation for all appropriate columns in all tables to a certain type (utf8_general_ci in my example below).

SELECT concat
        (
            'ALTER TABLE ', 
                t1.TABLE_SCHEMA, 
                '.', 
                t1.table_name, 
                ' MODIFY ', 
                t1.column_name, 
                ' ', 
                t1.data_type, 
                '(' , 
                    CHARACTER_MAXIMUM_LENGTH, 
                ')', 
                ' CHARACTER SET utf8 COLLATE utf8_general_ci;'
        )
from 
    information_schema.columns t1
where 
    t1.TABLE_SCHEMA like 'you_db_name_goes_here' AND
    t1.COLLATION_NAME IS NOT NULL AND
    t1.COLLATION_NAME NOT IN ('utf8_general_ci');

answered Mar 14, 2016 at 1:26

Parampal PooniParampal Pooni

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4

If you run phpMyAdmin >> select database >> select table >> go to "Operations" tab >> in "Table options" section >> you can pick Collation from the drop down list >> and once you press {Go} at the top of the screen you will see a message:

Your SQL query has been executed successfully

and a script

ALTER TABLE `tableName` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci 

But it will NOT change the collations of existing columns. To do so you can use this script (this one also came from phpMyAdmin)

ALTER TABLE  `tableName` CHANGE  `Name`  `Name` VARCHAR( 255 ) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL

answered Sep 4, 2015 at 4:34

Just run this SQL to convert all database tables at once. Change your COLLATION and databaseName to what you need.

SELECT CONCAT("ALTER TABLE ", TABLE_SCHEMA, '.', TABLE_NAME," COLLATE utf8_general_ci;") AS    ExecuteTheString
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA="databaseName"
AND TABLE_TYPE="BASE TABLE";

answered Oct 23, 2017 at 15:13

DzintarsDzintars

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Generates query to update each table and column of each table. I have used this to some of my projects before and was able to solved most of my COLLATION problems. (especially on JOINS)

To use, just export results to delimited text (probably new line '\n')

EACH TABLE

SELECT CONCAT('ALTER TABLE `', TABLE_NAME, 
              '` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;') 
       AS 'USE `DATABASE_NAME`;' 
FROM   INFORMATION_SCHEMA.TABLES 
WHERE  TABLE_SCHEMA = 'DATABASE_NAME' 
       AND TABLE_TYPE LIKE 'BASE TABLE' 

EACH COLUMN

SELECT CONCAT('ALTER TABLE `', TABLE_NAME, '` MODIFY COLUMN `', COLUMN_NAME,'` ', 
              DATA_TYPE, IF(CHARACTER_MAXIMUM_LENGTH IS NULL 
       OR DATA_TYPE LIKE 'longtext', '', CONCAT('(', CHARACTER_MAXIMUM_LENGTH, 
                                         ')') 
       ), ' COLLATE utf8mb4_unicode_ci;') AS 'USE `DATABASE_NAME`;' 
FROM   INFORMATION_SCHEMA.COLUMNS 
WHERE  TABLE_SCHEMA = 'DATABASE_NAME' 
       AND (SELECT INFORMATION_SCHEMA.TABLES.TABLE_TYPE 
            FROM   INFORMATION_SCHEMA.TABLES 
            WHERE  INFORMATION_SCHEMA.TABLES.TABLE_SCHEMA = 
                   INFORMATION_SCHEMA.COLUMNS.TABLE_SCHEMA 
                   AND INFORMATION_SCHEMA.TABLES.TABLE_NAME = 
                       INFORMATION_SCHEMA.COLUMNS.TABLE_NAME 
            LIMIT  1) LIKE 'BASE TABLE' 
       AND DATA_TYPE IN ( 'char', 'varchar' ) /* include other types if necessary */

gurkan

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answered Feb 27, 2021 at 9:04

SelSel

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You can change the CHARSET and COLLATION of all your tables through PHP script as follows. I like the answer of hkasera but the problem with it is that the query runs twice on each table. This code is almost the same except using MySqli instead of mysql and prevention of double querying. If I could vote up, I would have voted hkasera's answer up.

connect_errno){
    echo mysqli_connect_error();
    exit;
}
$res=$conn1->query("show tables") or die($conn1->error);
while($tables=$res->fetch_array()){
    $conn1->query("ALTER TABLE $tables[0] CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci") or die($conn1->error);
}
echo "The collation of your database has been successfully changed!";

$res->free();
$conn1->close();

?>

answered Feb 2, 2015 at 5:36

mtmehdimtmehdi

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1

You can simple add this code to script file

//Database Connection
$host = 'localhost';
$db_name = 'your_database_name';
$db_user =  'your_database_user_name';
$db_pass = 'your_database_user_password';

$con = mysql_connect($host,$db_user,$db_pass);

if(!$con) { echo "Cannot connect to the database ";die();}

  mysql_select_db($db_name);

  $result=mysql_query('show tables');

  while($tables = mysql_fetch_array($result)) {
    foreach ($tables as $key => $value) {
    mysql_query("ALTER TABLE $value CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci");
  }
}

echo "The collation of your database has been successfully changed!";

answered May 5, 2016 at 11:41

Chandra KumarChandra Kumar

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Better variant to generate SQL script by SQL request. It will not ruin defaults/nulls.

SELECT concat
    (
        'ALTER TABLE ', 
            t1.TABLE_SCHEMA, 
            '.', 
            t1.table_name, 
            ' MODIFY ', 
            t1.column_name, 
            ' ', 
            t1.column_type,
            ' CHARACTER SET utf8 COLLATE utf8_general_ci',
            if(t1.is_nullable='YES', ' NULL', ' NOT NULL'),
            if(t1.column_default is not null, concat(' DEFAULT \'', t1.column_default, '\''), ''),
            ';'
    )
from 
    information_schema.columns t1
where 
    t1.TABLE_SCHEMA like 'your_table_here' AND
    t1.COLLATION_NAME IS NOT NULL AND
    t1.COLLATION_NAME NOT IN ('utf8_general_ci');

answered Nov 4, 2019 at 13:37

1

I read it here, that you need to convert each table manually, it is not true. Here is a solution how to do it with a stored procedure:

DELIMITER $$

DROP PROCEDURE IF EXISTS changeCollation$$

-- character_set parameter could be 'utf8'
-- or 'latin1' or any other valid character set
CREATE PROCEDURE changeCollation(IN character_set VARCHAR(255))
BEGIN
DECLARE v_finished INTEGER DEFAULT 0;
DECLARE v_table_name varchar(255) DEFAULT "";
DECLARE v_message varchar(4000) DEFAULT "No records";

-- This will create a cursor that selects each table,
-- where the character set is not the one
-- that is defined in the parameter

DECLARE alter_cursor CURSOR FOR SELECT DISTINCT TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = DATABASE()
AND COLLATION_NAME NOT LIKE CONCAT(character_set, '_%');

-- This handler will set the value v_finished to 1
-- if there are no more rows

DECLARE CONTINUE HANDLER
FOR NOT FOUND SET v_finished = 1;

OPEN alter_cursor;

-- Start a loop to fetch each rows from the cursor
get_table: LOOP

-- Fetch the table names one by one
FETCH alter_cursor INTO v_table_name;

-- If there is no more record, then we have to skip
-- the commands inside the loop
IF v_finished = 1 THEN
LEAVE get_table;
END IF;

IF v_table_name != '' THEN

IF v_message = 'No records' THEN
SET v_message = '';
END IF;

-- This technic makes the trick, it prepares a statement
-- that is based on the v_table_name parameter and it means
-- that this one is different by each iteration inside the loop

SET @s = CONCAT('ALTER TABLE ',v_table_name,
' CONVERT TO CHARACTER SET ', character_set);
PREPARE stmt FROM @s;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SET v_message = CONCAT('The table ', v_table_name ,
' was changed to the default collation of ', character_set,
'.\n', v_message);

SET v_table_name = '';

END IF;
-- Close the loop and the cursor
END LOOP get_table;
CLOSE alter_cursor;

-- Returns information about the altered tables or 'No records'
SELECT v_message;

END $$

DELIMITER ;

After the procedure is created call it simply:

CALL changeCollation('utf8');

For more details read this blog.

Seybsen

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answered Jun 9, 2015 at 13:07

András OttóAndrás Ottó

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My solution is a combination of @Dzintars and @Quassnoi Answer.

SELECT CONCAT("ALTER TABLE ", TABLE_SCHEMA, '.', TABLE_NAME," CONVERT TO CHARACTER SET utf8mb4 ;") AS    ExecuteTheString
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA=""
AND TABLE_TYPE="BASE TABLE";

By using CONVERT TO, this generates a scripts, which converts all the Tables of to your requested encoding. This also changes the encoding of every column!

answered Nov 27, 2018 at 23:22

1

if you want to update the default charset on a schema:

 ALTER SCHEMA MYSCHEMA DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_unicode_ci;

answered Jul 31, 2017 at 3:44

Mircea StanciuMircea Stanciu

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I used the following shell script. It takes database name as a parameter and converts all tables to another charset and collation (given by another parameters or default value defined in the script).

#!/bin/bash

# mycollate.sh  [ ]
# changes MySQL/MariaDB charset and collation for one database - all tables and
# all columns in all tables

DB="$1"
CHARSET="$2"
COLL="$3"

[ -n "$DB" ] || exit 1
[ -n "$CHARSET" ] || CHARSET="utf8mb4"
[ -n "$COLL" ] || COLL="utf8mb4_general_ci"

echo $DB
echo "ALTER DATABASE $DB CHARACTER SET $CHARSET COLLATE $COLL;" | mysql

echo "USE $DB; SHOW TABLES;" | mysql -s | (
    while read TABLE; do
        echo $DB.$TABLE
        echo "ALTER TABLE $TABLE CONVERT TO CHARACTER SET $CHARSET COLLATE $COLL;" | mysql $DB
    done
)

answered Oct 11, 2017 at 10:52

Quick way - export to SQL file, use search and replace to change the text you need to change. Create new database, import the data and then rename the old database and the new one to the old name.

answered Nov 9, 2015 at 14:25

To change the collation of all fields in all tables of a database at once:

I was just adding another loop for the fields within the tables to the solution via Php before mentioned. This has helped, all fields in the tables are also converted.

 $table) {                   // for each table

    $sql = "ALTER TABLE $table CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci";
    echo "\n".$sql;
    mysql_query($sql);

    $sql = "show fields in ".$table." where type like 'varchar%' or type like 'char%' or type='text' or type='mediumtext';";
    $rs2=mysql_query($sql);
    while( $rw2 = mysql_fetch_array($rs2) ){            // for each field in table

        $sql = "ALTER TABLE `".$table."` CHANGE `".$rw2['Field']."` `".$rw2['Field']."` ".$rw2['Type']." CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL;";
        echo "\n".$sql;
        mysql_query($sql);

    } 


}
}
echo "The collation of your database has been successfully changed!";

?>}

answered May 1, 2020 at 21:42

Note, after changing the charset for database/table/column, you might need to actually convert the existing data (if you see, for example, something like "مطلوب توريد جÙ") with something like this:

update country set name = convert(cast(convert(name using latin1) as binary) using utf8), cn_flag = convert(cast(convert(cn_flag using latin1) as binary) using utf8), and so on..

While for converting database, tables and fields, I would suggest this answer from this thread which would generate a big set of queries that you will just copy at paste, here I couldn't find an automatic solution yet. Also be warned, if you will convert the same field twice you will get unrecoverable question marks: "???". You will also get this question marks if you will convert data before converting fields/tables.

answered Feb 11, 2021 at 11:57

user109764user109764

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I've just written a bash script to find all tables in a given database and covert them (and its columns).

Script is available here: https://github.com/Juddling/mysql-charset

answered Apr 19, 2019 at 2:34

JuddlingJuddling

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