How to convert all tables in database to one collation?

I'm getting error:

>Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '='"

I tried changing both tables manually to utf8_general_ci,IMPLICIT but I'm still getting the error.

Is there a way to convert all tables to utf8_general_ci,IMPLICIT and be done with it?

You need to execute a alter table statement for each table. The statement would follow this form:

ALTER TABLE tbl_name
[[DEFAULT] CHARACTER SET charset_name]
[COLLATE collation_name]

Now to get all the tables in the database you would need to execute the following query:

SELECT * 
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA="YourDataBaseName"
AND TABLE_TYPE="BASE TABLE";

So now let MySQL write the code for you:

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

You can copy the results and execute them. I have not tested the syntax but you should be able to figure out the rest. Think of it as a little exercise.

Hope That Helps!

Better option to change also collation of varchar columns inside table also

SELECT CONCAT('ALTER TABLE `', TABLE_NAME,'` CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;') AS    mySQL
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA= "myschema"
AND TABLE_TYPE="BASE TABLE"

Additionnaly if you have data with forein key on non utf8 column before launch the bunch script use

SET foreign_key_checks = 0;

It means global SQL will be for mySQL :

SET foreign_key_checks = 0;
ALTER TABLE `table1` CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
ALTER TABLE `table2` CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
ALTER TABLE `tableXXX` CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
SET foreign_key_checks = 1;

But take care if according mysql documentation http://dev.mysql.com/doc/refman/5.1/en/charset-column.html,

> If you use ALTER TABLE to convert a column from one character set to another, MySQL attempts to map the data values, but if the character sets are incompatible, there may be data loss. "

EDIT: Specially with column type enum, it just crash completly enums set (even if there is no special caracters) https://bugs.mysql.com/bug.php?id=26731

@Namphibian's suggestion helped me a lot...
went a little further though and added columns and views to the script

just enter your schema's name below and it will do the rest

-- set your table name here
SET @MY_SCHEMA = "";

-- tables
SELECT DISTINCT
	CONCAT("ALTER TABLE ", TABLE_NAME," CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;") as queries
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA=@MY_SCHEMA
  AND TABLE_TYPE="BASE TABLE"

UNION

-- table columns
SELECT DISTINCT
	CONCAT("ALTER TABLE ", C.TABLE_NAME, " CHANGE ", C.COLUMN_NAME, " ", C.COLUMN_NAME, " ", C.COLUMN_TYPE, " CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;") as queries
FROM INFORMATION_SCHEMA.COLUMNS as C
	LEFT JOIN INFORMATION_SCHEMA.TABLES as T
		ON C.TABLE_NAME = T.TABLE_NAME
WHERE C.COLLATION_NAME is not null
	AND C.TABLE_SCHEMA=@MY_SCHEMA
	AND T.TABLE_TYPE="BASE TABLE"

UNION

-- views
SELECT DISTINCT
	CONCAT("CREATE OR REPLACE VIEW ", V.TABLE_NAME, " AS ", V.VIEW_DEFINITION, ";") as queries
FROM INFORMATION_SCHEMA.VIEWS as V
	LEFT JOIN INFORMATION_SCHEMA.TABLES as T
		ON V.TABLE_NAME = T.TABLE_NAME
WHERE V.TABLE_SCHEMA=@MY_SCHEMA
	AND T.TABLE_TYPE="VIEW";

Below is the more accurate query. I am giving example how to convert it to utf8

SELECT CONCAT("ALTER TABLE `", TABLE_NAME,"` DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci;") AS    mySQL
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA="myschema"
AND TABLE_TYPE="BASE TABLE"

If you're using PhpMyAdmin, you can now:

1. Select the database.
2. Click the "Operations" tab.
3. Under "Collation" section, select the desired collation.
4. Click the "Change all tables collations" checkbox.
5. A new "Change all tables columns collations" checkbox will appear.
6. Click the "Change all tables columns collations" checkbox.
7. Click the "Go" button.

I had over 250 tables to convert. It took a little over 5 minutes.

You can use this BASH script:

#!/bin/bash

USER="YOUR_DATABASE_USER"
PASSWORD="YOUR_USER_PASSWORD"
DB_NAME="DATABASE_NAME"
CHARACTER_SET="utf8" # your default character set
COLLATE="utf8_general_ci" # your default collation

tables=`mysql -u $USER -p$PASSWORD -e "SELECT tbl.TABLE_NAME FROM information_schema.TABLES tbl WHERE tbl.TABLE_SCHEMA = '$DB_NAME' AND tbl.TABLE_TYPE='BASE TABLE'"`

for tableName in $tables; do
    if [[ "$tableName" != "TABLE_NAME" ]] ; then
        mysql -u $USER -p$PASSWORD -e "ALTER TABLE $DB_NAME.$tableName DEFAULT CHARACTER SET $CHARACTER_SET COLLATE $COLLATE;"
        echo "$tableName - done"
    fi
done

For phpMyAdmin I figured this out:

SELECT GROUP_CONCAT("ALTER TABLE ", TABLE_SCHEMA, '.', TABLE_NAME," CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;" SEPARATOR ' ') AS    OneSQLString
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA="yourtableschemaname"
AND TABLE_TYPE="BASE TABLE"

Just change yourtableschemaname and you're fine.

This is my version of a bash 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
)

Taking the answer from @Petr Stastny a step further by adding a password variable. I'd prefer if it actually took it in like a regular password rather than as an argument, but it's working for what I needed.

#!/bin/bash

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

DB="$1"
PW="$2"
CHARSET="$3"
COLL="$4"

[ -n "$DB" ] || exit 1
[ -n "$PW" ]
[ -n "$CHARSET" ] || CHARSET="utf8mb4"
[ -n "$COLL" ] || COLL="utf8mb4_bin"

PW="--password=""$PW"

echo $DB
echo "ALTER DATABASE $DB CHARACTER SET $CHARSET COLLATE $COLL;" | mysql -u root "$PW"

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

PW="pleaseEmptyMeNow"

Following on from G H I've added the user and host parameters incase you need to do this on a remote server

	#!/bin/bash

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

	DB="$1"
	USER="$2"
	PW="$3"
	HOST="$4"
	CHARSET="$5"
	COLL="$6"

	[ -n "$DB" ] || exit 1
	[ -n "$USER" ] || exit 1
	[ -n "$PW" ] || exit 1
	[ -n "$HOST" ] || HOST="localhost"
	[ -n "$CHARSET" ] || CHARSET="utf8mb4"
	[ -n "$COLL" ] || COLL="utf8mb4_general_ci"

	PW="--password=""$PW"
	HOST="--host=""$HOST"
	USER="--user=""$USER"

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

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

	PW="pleaseEmptyMeNow"

If you want a copy-paste bash script:

var=$(mysql -e 'SELECT CONCAT("ALTER TABLE ", TABLE_NAME," CONVERT TO CHARACTER SET utf8 COLLATE utf8_czech_ci;") AS execTabs FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA="zabbix" AND TABLE_TYPE="BASE TABLE"' -uroot -p )

var+='ALTER DATABASE zabbix CHARACTER SET utf8 COLLATE utf8_general_ci;'

echo $var | cut -d " " -f2- | mysql -uroot -p zabbix

Change zabbix to your database name.

I will share my answer using MySQL procedure. You need to run 3 sql command.

1.

DROP PROCEDURE IF EXISTS UpdateTable;

2.

DELIMITER $$

CREATE PROCEDURE UpdateTable()
BEGIN

	DECLARE done INT DEFAULT FALSE;
	DECLARE _table_name CHAR(255);
	DECLARE cur CURSOR FOR
           	SELECT table_name FROM information_schema.tables
			WHERE table_schema = 'my_db_name' AND table_type = "BASE TABLE";
	DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur;
	My_loop: LOOP
	    FETCH cur INTO _table_name;
		SET @my_table_name = _table_name;

	    IF done THEN
	      LEAVE My_loop;
	    END IF;

		SET FOREIGN_KEY_CHECKS = 0;

		SET @stmt = CONCAT('ALTER TABLE ', @my_table_name, ' CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;'); 
		PREPARE stmt1 FROM @stmt; 
		EXECUTE stmt1; 
		DEALLOCATE PREPARE stmt1;	
		
		SET FOREIGN_KEY_CHECKS = 1;
			
	END LOOP;
	CLOSE cur;

END$$

DELIMITER ;

3.

CALL UpdateTable();

Then run first one again. If you don't want to store the procedure.