mysql – How to change collation of database, table, column?

The Question :

221 people think this question is useful

The database is latin1_general_ci now and I want to change collation to utf8mb4_general_ci.

Is there any setting in PhpMyAdmin to change collation of database, table, column? Rather than changing one by one?

The Question Comments :

The Answer 1

272 people think this answer is useful

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.

The Answer 2

244 people think this answer is useful

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 <database_name> CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Changing it per table:

ALTER TABLE <table_name> 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 <table_name> MODIFY <column_name> VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

The Answer 3

68 people think this answer is useful

You can run a php script.

               <?php
                   $con = mysql_connect('localhost','user','password');
                   if(!$con) { echo "Cannot connect to the database ";die();}
                   mysql_select_db('dbname');
                   $result=mysql_query('show tables');
                   while($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!";
                ?>

The Answer 4

46 people think this answer is useful

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.

The Answer 5

18 people think this answer is useful

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');

The Answer 6

11 people think this answer is useful

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

The Answer 7

9 people think this answer is useful

you can set default collation at several levels:

http://dev.mysql.com/doc/refman/5.0/en/charset-syntax.html

1) client 2) server default 3) database default 4) table default 5) column

The Answer 8

6 people think this answer is useful

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";

The Answer 9

4 people think this answer is useful

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.

<?php
$conn1=new MySQLi("localhost","user","password","database");
if($conn1->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();

?>

The Answer 10

4 people think this answer is useful

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!";

The Answer 11

4 people think this answer is useful

I was surprised to learn, and so I had to come back here and report, that the excellent and well maintained Interconnect/it SAFE SEARCH AND REPLACE ON DATABASE script has some options for converting tables to utf8 / unicode, and even to convert to innodb. It’s a script commonly used to migrate a database driven website (WordPress, Drupal, Joomla, etc) from one domain to another.

interconnect script buttons

The Answer 12

3 people think this answer is useful

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.

The Answer 13

2 people think this answer is useful

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

 ALTER SCHEMA MYSCHEMA DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_unicode_ci;

The Answer 14

2 people think this answer is useful

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');

The Answer 15

1 people think this answer is useful

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 <database> [<charset> <collation>]
# 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
)

The Answer 16

1 people think this answer is useful

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="<your-database>"
AND TABLE_TYPE="BASE TABLE";

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

The Answer 17

0 people think this answer is useful

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.

The Answer 18

0 people think this answer is useful

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.

<?php
$con = mysql_connect('localhost','user','pw');
if(!$con) { echo "Cannot connect to the database ";die();}
mysql_select_db('database_name');
$result=mysql_query('show tables');
while($tables = mysql_fetch_array($result)) {

foreach ($tables as $key => $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!";

?>}

The Answer 19

-1 people think this answer is useful

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

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